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|
@extends('template')
@section('content')
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<title>psql quick reference</title>
<link href="https://fonts.googleapis.com/css2?family=Berkeley+Mono&family=Inter:wght@400;500&display=swap" rel="stylesheet">
<style>
* { box-sizing: border-box; margin: 0; padding: 0; }
body {
background: #1e2128;
color: #cdd3de;
font-family: 'Inter', sans-serif;
font-size: 14px;
line-height: 1.6;
}
.page {
max-width: 1400px;
margin: 0 auto;
}
/* ── HEADER ── */
h1 {
font-family: 'Berkeley Mono', monospace;
font-size: 28px;
font-weight: 400;
color: #7dd3db;
letter-spacing: -0.5px;
margin-bottom: 4px;
}
.subtitle {
font-size: 13px;
color: #5a6270;
margin-bottom: 32px;
}
/* ── TOC ── */
.toc {
background: #252830;
border: 1px solid #2e3340;
border-radius: 6px;
padding: 16px 20px;
margin-bottom: 40px;
}
.toc-label {
font-family: 'Berkeley Mono', monospace;
font-size: 11px;
color: #5a6270;
text-transform: uppercase;
letter-spacing: 0.08em;
margin-bottom: 10px;
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.toc-links {
display: flex;
flex-direction: column;
gap: 4px;
width: fit-content;
}
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font-family: 'Berkeley Mono', monospace;
font-size: 12px;
color: #7dd3db;
text-decoration: none;
background: #1e2128;
border: 1px solid #2e3340;
padding: 3px 10px;
border-radius: 4px;
}
.toc-links a:hover { border-color: #7dd3db; }
/* ── TWO-COLUMN AREA ── */
.two-col {
display: grid;
grid-template-columns: 1fr 1fr;
gap: 16px;
margin-bottom: 16px;
}
/* ── SECTION (full width) ── */
.section {
width: 100%;
background: #252830;
border: 1px solid #2e3340;
border-radius: 6px;
overflow: hidden;
margin-bottom: 16px;
scroll-margin-top: 24px;
}
/* cards inside two-col don't need bottom margin */
.two-col .section { margin-bottom: 0; }
.section-head {
display: flex;
align-items: center;
gap: 8px;
padding: 10px 16px;
background: #2a2e38;
border-bottom: 1px solid #2e3340;
}
.section-head h2 {
font-family: 'Berkeley Mono', monospace;
font-size: 11px;
font-weight: 400;
color: #5a6270;
letter-spacing: 0.1em;
text-transform: uppercase;
flex: 1;
}
.dot {
width: 8px;
height: 8px;
border-radius: 50%;
flex-shrink: 0;
}
.back {
font-family: 'Berkeley Mono', monospace;
font-size: 11px;
color: #5a6270;
text-decoration: none;
padding: 2px 6px;
border: 1px solid #2e3340;
border-radius: 3px;
}
.back:hover { color: #7dd3db; border-color: #7dd3db; }
/* ── REFERENCE TABLE ── */
.ref-table {
width: 100%;
border-collapse: collapse;
}
.ref-table td {
padding: 7px 16px;
vertical-align: top;
border-bottom: 1px solid #2e3340;
font-size: 13px;
}
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font-family: 'Berkeley Mono', monospace;
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.ref-table .section-row td {
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font-family: 'Berkeley Mono', monospace;
font-size: 10px;
color: #5a6270;
text-transform: uppercase;
letter-spacing: 0.08em;
background: #2a2e38;
border-bottom: 1px solid #2e3340;
}
/* ── CODE BLOCKS ── */
.code-grid {
display: grid;
grid-template-columns: 1fr 1fr;
}
.code-block {
padding: 14px 16px;
border-right: 1px solid #2e3340;
border-bottom: 1px solid #2e3340;
font-family: 'Berkeley Mono', monospace;
font-size: 12px;
line-height: 1.85;
background: #1e2128;
}
.code-block:nth-child(even) { border-right: none; }
/* last row: remove bottom borders */
.code-block:nth-last-child(1),
.code-block:nth-last-child(2) { border-bottom: none; }
/* if odd number, last item spans or just loses bottom */
.code-block:only-child { grid-column: 1 / -1; border-right: none; border-bottom: none; }
.lbl {
display: block;
font-size: 10px;
color: #fffc41fa;
text-transform: uppercase;
letter-spacing: 0.07em;
margin-bottom: 6px;
}
/* ── SYNTAX COLORS ── */
.kw { color: #6fa8e8; }
.fn { color: #c792ea; }
.str { color: #88cc88; }
.num { color: #f0a070; }
.cmt { color: #4a5262; font-style: italic; }
.op { color: #7dd3db; }
.typ { color: #e5c07b; }
.cmd { color: #7dd3db; }
.tbl { color: #f0a070; }
/* ── JOIN VISUAL ── */
.join-grid {
display: grid;
grid-template-columns: repeat(6, 1fr);
gap: 1px;
background: #2e3340;
border-top: 1px solid #2e3340;
}
.join-cell {
background: #1e2128;
padding: 12px 14px;
}
.join-name {
font-family: 'Berkeley Mono', monospace;
font-size: 11px;
color: #7dd3db;
margin-bottom: 4px;
margin-top: 4px;
}
.join-desc { font-size: 11px; color: #5a6270; line-height: 1.5; }
.venn { display: flex; align-items: center; margin-bottom: 6px; }
.c { width: 20px; height: 20px; border-radius: 50%; border: 1.5px solid; flex-shrink: 0; }
.cL { border-color: #6fa8e8; margin-right: -6px; }
.cR { border-color: #f0a070; }
.fL { background: rgba(111,168,232,0.3); }
.fR { background: rgba(240,160,112,0.3); }
.fB { background: rgba(160,140,200,0.3); }
/* ── PILLS ── */
.pill {
font-family: 'Berkeley Mono', monospace;
font-size: 11px;
padding: 1px 8px;
border-radius: 3px;
}
.p-blue { background: #1a2a3a; color: #6fa8e8; }
.p-yellow { background: #2e2412; color: #e5c07b; }
.p-red { background: #2e1818; color: #e06c75; }
/* ── JSONB split ── */
.split {
display: grid;
grid-template-columns: 1fr 1fr;
border-top: 1px solid #2e3340;
}
.split > *:first-child { border-right: 1px solid #2e3340; }
footer {
margin-top: 48px;
font-family: 'Berkeley Mono', monospace;
font-size: 11px;
color: #3a4050;
text-align: center;
}
</style>
</head>
<body>
<div class="page">
<h1>psql</h1>
<div class="subtitle">PostgreSQL 16 quick reference · <a href="https://postgresql.org/docs" style="color:#5a6270">postgresql.org/docs</a></div>
<!-- TOC -->
<div class="toc" id="top">
<div class="toc-label">sections</div>
<div class="toc-links">
<a href="#meta">meta-commands</a>
<a href="#types">data types</a>
<a href="#ddl">DDL</a>
<a href="#dml">DML</a>
<a href="#select">SELECT</a>
<a href="#functions">functions</a>
<a href="#joins">joins</a>
<a href="#users">users & perms</a>
<a href="#transactions">transactions</a>
<a href="#explain">explain & analyze</a>
<a href="#admin">admin queries</a>
<a href="#jsonb">jsonb</a>
<a href="#conditional">conditional & casting</a>
</div>
</div>
<!-- two-col: meta + types -->
<div class="two-col">
<div class="section" id="meta">
<div class="section-head">
<span class="dot" style="background:#7dd3db"></span>
<h2>meta-commands ( \ )</h2>
<a class="back" href="#top">↑</a>
</div>
<table class="ref-table">
<tr><td><span class="cmd">\l</span></td><td>list databases</td></tr>
<tr><td><span class="cmd">\c dbname</span></td><td>connect to database</td></tr>
<tr><td><span class="cmd">\dt</span></td><td>list tables in schema</td></tr>
<tr><td><span class="cmd">\d table</span></td><td>describe table</td></tr>
<tr><td><span class="cmd">\di</span></td><td>list indexes</td></tr>
<tr><td><span class="cmd">\dv</span></td><td>list views</td></tr>
<tr><td><span class="cmd">\df</span></td><td>list functions</td></tr>
<tr><td><span class="cmd">\dn</span></td><td>list schemas</td></tr>
<tr><td><span class="cmd">\du</span></td><td>list roles / users</td></tr>
<tr><td><span class="cmd">\dp table</span></td><td>show privileges</td></tr>
<tr><td><span class="cmd">\timing</span></td><td>toggle execution time</td></tr>
<tr><td><span class="cmd">\x</span></td><td>toggle expanded output</td></tr>
<tr><td><span class="cmd">\e</span></td><td>open query in $EDITOR</td></tr>
<tr><td><span class="cmd">\i file.sql</span></td><td>execute sql file</td></tr>
<tr><td><span class="cmd">\o file</span></td><td>pipe output to file</td></tr>
<tr><td><span class="cmd">\q</span></td><td>quit</td></tr>
</table>
</div>
<div class="section" id="types">
<div class="section-head">
<span class="dot" style="background:#e5c07b"></span>
<h2>data types</h2>
<a class="back" href="#top">↑</a>
</div>
<table class="ref-table">
<tr><td><span class="typ">integer</span> / <span class="typ">int</span></td><td>4-byte signed int</td></tr>
<tr><td><span class="typ">bigint</span></td><td>8-byte signed int</td></tr>
<tr><td><span class="typ">smallint</span></td><td>2-byte signed int</td></tr>
<tr><td><span class="typ">serial</span> / <span class="typ">bigserial</span></td><td>auto-incrementing int</td></tr>
<tr><td><span class="typ">numeric(p,s)</span></td><td>exact decimal</td></tr>
<tr><td><span class="typ">real</span> / <span class="typ">float8</span></td><td>4/8-byte float</td></tr>
<tr><td><span class="typ">boolean</span></td><td>true / false / null</td></tr>
<tr><td><span class="typ">varchar(n)</span></td><td>variable string, limit n</td></tr>
<tr><td><span class="typ">text</span></td><td>unlimited string</td></tr>
<tr><td><span class="typ">bytea</span></td><td>binary data</td></tr>
<tr><td><span class="typ">date</span></td><td>calendar date</td></tr>
<tr><td><span class="typ">time</span></td><td>time of day</td></tr>
<tr><td><span class="typ">timestamp</span></td><td>date + time (no tz)</td></tr>
<tr><td><span class="typ">timestamptz</span></td><td>date + time with tz</td></tr>
<tr><td><span class="typ">interval</span></td><td>time span</td></tr>
<tr><td><span class="typ">uuid</span></td><td>universally unique id</td></tr>
<tr><td><span class="typ">json</span> / <span class="typ">jsonb</span></td><td>json (jsonb = binary)</td></tr>
<tr><td><span class="typ">int[]</span> / <span class="typ">text[]</span></td><td>arrays of any type</td></tr>
</table>
</div>
</div><!-- end two-col -->
<!-- DDL — full width -->
<div class="section" id="ddl">
<div class="section-head">
<span class="dot" style="background:#6fa8e8"></span>
<h2>DDL — define</h2>
<a class="back" href="#top">↑</a>
</div>
<div class="code-grid">
<div class="code-block">
<span class="lbl">create table</span>
<span class="kw">CREATE TABLE</span> <span class="tbl">users</span> (<br>
id <span class="typ">bigserial</span> <span class="kw">PRIMARY KEY</span>,<br>
username <span class="typ">text</span> <span class="kw">NOT NULL UNIQUE</span>,<br>
email <span class="typ">text</span> <span class="kw">NOT NULL</span>,<br>
created_at <span class="typ">timestamptz</span> <span class="kw">DEFAULT</span> <span class="fn">now</span>()<br>
);
</div>
<div class="code-block">
<span class="lbl">alter table</span>
<span class="kw">ALTER TABLE</span> <span class="tbl">users</span> <span class="kw">ADD COLUMN</span> bio <span class="typ">text</span>;<br>
<span class="kw">ALTER TABLE</span> <span class="tbl">users</span> <span class="kw">DROP COLUMN</span> bio;<br>
<span class="kw">ALTER TABLE</span> <span class="tbl">users</span> <span class="kw">RENAME COLUMN</span> email <span class="kw">TO</span> mail;<br>
<span class="kw">ALTER TABLE</span> <span class="tbl">users</span> <span class="kw">ALTER COLUMN</span> bio <span class="kw">SET NOT NULL</span>;<br>
<span class="kw">ALTER TABLE</span> <span class="tbl">users</span> <span class="kw">RENAME TO</span> <span class="tbl">accounts</span>;
</div>
<div class="code-block">
<span class="lbl">indexes</span>
<span class="kw">CREATE INDEX</span> idx_email <span class="kw">ON</span> <span class="tbl">users</span>(email);<br>
<span class="kw">CREATE UNIQUE INDEX ON</span> <span class="tbl">users</span>(username);<br>
<span class="kw">CREATE INDEX ON</span> <span class="tbl">users</span> <span class="kw">USING</span> gin(data);<br>
<span class="kw">CREATE INDEX CONCURRENTLY ON</span> <span class="tbl">users</span>(email);<br>
<span class="kw">DROP INDEX</span> idx_email;
</div>
<div class="code-block">
<span class="lbl">foreign key</span>
<span class="kw">ALTER TABLE</span> <span class="tbl">posts</span> <span class="kw">ADD CONSTRAINT</span> fk_user<br>
<span class="kw">FOREIGN KEY</span>(user_id)<br>
<span class="kw">REFERENCES</span> <span class="tbl">users</span>(id)<br>
<span class="kw">ON DELETE CASCADE</span>;
</div>
</div>
</div>
<!-- DML — full width -->
<div class="section" id="dml">
<div class="section-head">
<span class="dot" style="background:#88cc88"></span>
<h2>DML — manipulate</h2>
<a class="back" href="#top">↑</a>
</div>
<div class="code-grid">
<div class="code-block">
<span class="lbl">insert</span>
<span class="kw">INSERT INTO</span> <span class="tbl">users</span> (username, email)<br>
<span class="kw">VALUES</span> (<span class="str">'alice'</span>, <span class="str">'alice@example.com'</span>)<br>
<span class="kw">RETURNING</span> id, created_at;
</div>
<div class="code-block">
<span class="lbl">upsert</span>
<span class="kw">INSERT INTO</span> <span class="tbl">users</span> (username, email)<br>
<span class="kw">VALUES</span> (<span class="str">'alice'</span>, <span class="str">'alice@example.com'</span>)<br>
<span class="kw">ON CONFLICT</span>(username) <span class="kw">DO UPDATE SET</span><br>
email <span class="op">=</span> <span class="kw">EXCLUDED</span>.email;
</div>
<div class="code-block">
<span class="lbl">update</span>
<span class="kw">UPDATE</span> <span class="tbl">users</span> <span class="kw">SET</span> email <span class="op">=</span> <span class="str">'x@y.com'</span><br>
<span class="kw">WHERE</span> id <span class="op">=</span> <span class="num">42</span><br>
<span class="kw">RETURNING</span> *;
</div>
<div class="code-block">
<span class="lbl">update from join</span>
<span class="kw">UPDATE</span> <span class="tbl">users</span> u<br>
<span class="kw">SET</span> score <span class="op">=</span> s.score<br>
<span class="kw">FROM</span> <span class="tbl">scores</span> s<br>
<span class="kw">WHERE</span> s.user_id <span class="op">=</span> u.id;
</div>
<div class="code-block">
<span class="lbl">delete / truncate</span>
<span class="kw">DELETE FROM</span> <span class="tbl">users</span> <span class="kw">WHERE</span> id <span class="op">=</span> <span class="num">42</span>;<br>
<span class="kw">TRUNCATE TABLE</span> <span class="tbl">users</span><br>
<span class="kw">RESTART IDENTITY CASCADE</span>;
</div>
<div class="code-block">
<span class="lbl">copy (bulk import / export)</span>
<span class="kw">COPY</span> <span class="tbl">users</span> <span class="kw">FROM</span> <span class="str">'/tmp/in.csv'</span> CSV HEADER;<br>
<span class="kw">COPY</span> <span class="tbl">users</span> <span class="kw">TO</span> <span class="str">'/tmp/out.csv'</span> CSV HEADER;
</div>
</div>
</div>
<!-- SELECT — full width -->
<div class="section" id="select">
<div class="section-head">
<span class="dot" style="background:#c792ea"></span>
<h2>SELECT anatomy</h2>
<a class="back" href="#top">↑</a>
</div>
<div class="code-grid">
<div class="code-block">
<span class="lbl">group / order / limit</span>
<span class="kw">SELECT</span> u.id, <span class="fn">count</span>(p.id) <span class="kw">AS</span> posts<br>
<span class="kw">FROM</span> <span class="tbl">users</span> u<br>
<span class="kw">LEFT JOIN</span> <span class="tbl">posts</span> p <span class="kw">ON</span> p.user_id <span class="op">=</span> u.id<br>
<span class="kw">WHERE</span> u.created_at <span class="op">></span> <span class="str">'2024-01-01'</span><br>
<span class="kw">GROUP BY</span> u.id<br>
<span class="kw">HAVING</span> <span class="fn">count</span>(p.id) <span class="op">></span> <span class="num">5</span><br>
<span class="kw">ORDER BY</span> posts <span class="kw">DESC</span><br>
<span class="kw">LIMIT</span> <span class="num">10</span> <span class="kw">OFFSET</span> <span class="num">20</span>;
</div>
<div class="code-block">
<span class="lbl">window functions</span>
<span class="kw">SELECT</span> username,<br>
<span class="fn">row_number</span>() <span class="kw">OVER</span> (<span class="kw">ORDER BY</span> created_at),<br>
<span class="fn">rank</span>() <span class="kw">OVER</span> (<span class="kw">PARTITION BY</span> role <span class="kw">ORDER BY</span> score <span class="kw">DESC</span>),<br>
<span class="fn">lag</span>(score) <span class="kw">OVER</span> (<span class="kw">ORDER BY</span> created_at),<br>
<span class="fn">sum</span>(score) <span class="kw">OVER</span> (<span class="kw">PARTITION BY</span> role)<br>
<span class="kw">FROM</span> <span class="tbl">users</span>;
</div>
<div class="code-block">
<span class="lbl">CTE</span>
<span class="kw">WITH</span> active <span class="kw">AS</span> (<br>
<span class="kw">SELECT</span> * <span class="kw">FROM</span> <span class="tbl">users</span> <span class="kw">WHERE</span> active <span class="op">=</span> <span class="kw">true</span><br>
),<br>
ranked <span class="kw">AS</span> (<br>
<span class="kw">SELECT</span> *, <span class="fn">row_number</span>() <span class="kw">OVER</span> (<span class="kw">ORDER BY</span> score) rn<br>
<span class="kw">FROM</span> active<br>
)<br>
<span class="kw">SELECT</span> * <span class="kw">FROM</span> ranked <span class="kw">WHERE</span> rn <span class="op"><=</span> <span class="num">10</span>;
</div>
<div class="code-block">
<span class="lbl">subquery / exists</span>
<span class="kw">SELECT</span> * <span class="kw">FROM</span> <span class="tbl">users</span> <span class="kw">WHERE</span> id <span class="kw">IN</span> (<br>
<span class="kw">SELECT</span> user_id <span class="kw">FROM</span> <span class="tbl">posts</span><br>
<span class="kw">WHERE</span> published <span class="op">=</span> <span class="kw">true</span><br>
);<br><br>
<span class="kw">SELECT</span> * <span class="kw">FROM</span> <span class="tbl">users</span> u <span class="kw">WHERE EXISTS</span> (<br>
<span class="kw">SELECT</span> <span class="num">1</span> <span class="kw">FROM</span> <span class="tbl">posts</span> p <span class="kw">WHERE</span> p.user_id <span class="op">=</span> u.id<br>
);
</div>
</div>
</div>
<!-- functions — full width -->
<div class="section" id="functions">
<div class="section-head">
<span class="dot" style="background:#f0a070"></span>
<h2>functions</h2>
<a class="back" href="#top">↑</a>
</div>
<table class="ref-table">
<tr class="section-row"><td colspan="2">aggregate</td></tr>
<tr><td><span class="fn">count</span>(*)</td><td>row count</td></tr>
<tr><td><span class="fn">sum</span>(col) / <span class="fn">avg</span>(col)</td><td>sum / average</td></tr>
<tr><td><span class="fn">min</span>(col) / <span class="fn">max</span>(col)</td><td>min / max value</td></tr>
<tr><td><span class="fn">string_agg</span>(col, sep)</td><td>concatenate to string</td></tr>
<tr><td><span class="fn">array_agg</span>(col)</td><td>collect into array</td></tr>
<tr><td><span class="fn">json_agg</span>(col)</td><td>collect into json array</td></tr>
<tr class="section-row"><td colspan="2">string</td></tr>
<tr><td><span class="fn">length</span>(str)</td><td>character count</td></tr>
<tr><td><span class="fn">lower</span> / <span class="fn">upper</span>(str)</td><td>case conversion</td></tr>
<tr><td><span class="fn">trim</span>(str)</td><td>strip whitespace</td></tr>
<tr><td><span class="fn">substring</span>(str, pos, len)</td><td>extract substring</td></tr>
<tr><td><span class="fn">replace</span>(str, from, to)</td><td>replace occurrence</td></tr>
<tr><td><span class="fn">split_part</span>(str, delim, n)</td><td>split and pick nth part</td></tr>
<tr><td><span class="fn">regexp_replace</span>(str, pat, rep)</td><td>regex substitution</td></tr>
<tr><td><span class="fn">concat</span>(a, b, ...)</td><td>concatenate (nulls skipped)</td></tr>
<tr class="section-row"><td colspan="2">date / time</td></tr>
<tr><td><span class="fn">now</span>()</td><td>current timestamp with tz</td></tr>
<tr><td><span class="fn">current_date</span></td><td>today's date</td></tr>
<tr><td><span class="fn">date_trunc</span>(<span class="str">'month'</span>, ts)</td><td>truncate to unit</td></tr>
<tr><td><span class="fn">extract</span>(year <span class="kw">FROM</span> ts)</td><td>extract part</td></tr>
<tr><td><span class="fn">age</span>(ts1, ts2)</td><td>interval between timestamps</td></tr>
<tr class="section-row"><td colspan="2">math & misc</td></tr>
<tr><td><span class="fn">abs</span> / <span class="fn">ceil</span> / <span class="fn">floor</span>(n)</td><td>absolute / ceiling / floor</td></tr>
<tr><td><span class="fn">round</span>(n, d)</td><td>round to d decimal places</td></tr>
<tr><td><span class="fn">random</span>()</td><td>random float 0.0–1.0</td></tr>
<tr><td><span class="fn">gen_random_uuid</span>()</td><td>generate v4 uuid</td></tr>
</table>
</div>
<!-- joins — full width -->
<div class="section" id="joins">
<div class="section-head">
<span class="dot" style="background:#e06c75"></span>
<h2>joins</h2>
<a class="back" href="#top">↑</a>
</div>
<div class="join-grid">
<div class="join-cell">
<div class="venn"><div class="c cL fB"></div><div class="c cR fB"></div></div>
<div class="join-name">INNER JOIN</div>
<div class="join-desc">matching rows in both tables</div>
</div>
<div class="join-cell">
<div class="venn"><div class="c cL fL"></div><div class="c cR"></div></div>
<div class="join-name">LEFT JOIN</div>
<div class="join-desc">all left rows, null if no right match</div>
</div>
<div class="join-cell">
<div class="venn"><div class="c cL"></div><div class="c cR fR"></div></div>
<div class="join-name">RIGHT JOIN</div>
<div class="join-desc">all right rows, null if no left match</div>
</div>
<div class="join-cell">
<div class="venn"><div class="c cL fL"></div><div class="c cR fR"></div></div>
<div class="join-name">FULL OUTER JOIN</div>
<div class="join-desc">all rows, nulls where no match</div>
</div>
<div class="join-cell">
<div class="venn" style="gap:8px"><div class="c cL" style="margin:0"></div><div class="c cR"></div></div>
<div class="join-name">CROSS JOIN</div>
<div class="join-desc">every left row × every right row</div>
</div>
<div class="join-cell">
<div class="venn"><div class="c cL fL" style="margin:0"></div><div class="c cR" style="margin-left:-6px"></div></div>
<div class="join-name">ANTI-JOIN</div>
<div class="join-desc">LEFT JOIN … WHERE right IS NULL</div>
</div>
</div>
<div class="code-grid">
<div class="code-block">
<span class="lbl">standard syntax</span>
<span class="kw">SELECT</span> u.username, p.title<br>
<span class="kw">FROM</span> <span class="tbl">users</span> u<br>
<span class="kw">INNER JOIN</span> <span class="tbl">posts</span> p <span class="kw">ON</span> p.user_id <span class="op">=</span> u.id;
</div>
<div class="code-block">
<span class="lbl">anti-join pattern</span>
<span class="kw">SELECT</span> * <span class="kw">FROM</span> <span class="tbl">users</span> u<br>
<span class="kw">LEFT JOIN</span> <span class="tbl">posts</span> p <span class="kw">ON</span> p.user_id <span class="op">=</span> u.id<br>
<span class="kw">WHERE</span> p.id <span class="kw">IS NULL</span>;
</div>
</div>
</div>
<!-- users — full width -->
<div class="section" id="users">
<div class="section-head">
<span class="dot" style="background:#e5c07b"></span>
<h2>users & permissions</h2>
<a class="back" href="#top">↑</a>
</div>
<div class="code-grid">
<div class="code-block">
<span class="lbl">create user / role</span>
<span class="kw">CREATE USER</span> alice <span class="kw">WITH PASSWORD</span> <span class="str">'secret'</span>;<br>
<span class="kw">CREATE ROLE</span> readonly;<br>
<span class="kw">GRANT</span> readonly <span class="kw">TO</span> alice;
</div>
<div class="code-block">
<span class="lbl">grant / revoke</span>
<span class="kw">GRANT ALL PRIVILEGES ON DATABASE</span> mydb <span class="kw">TO</span> alice;<br>
<span class="kw">GRANT SELECT ON ALL TABLES IN SCHEMA</span> public <span class="kw">TO</span> alice;<br>
<span class="kw">GRANT USAGE ON SCHEMA</span> public <span class="kw">TO</span> alice;<br>
<span class="kw">REVOKE ALL ON</span> <span class="tbl">users</span> <span class="kw">FROM</span> alice;
</div>
<div class="code-block">
<span class="lbl">alter user</span>
<span class="kw">ALTER USER</span> alice <span class="kw">WITH PASSWORD</span> <span class="str">'newpass'</span>;<br>
<span class="kw">ALTER USER</span> alice <span class="kw">WITH SUPERUSER</span>;<br>
<span class="kw">ALTER USER</span> alice <span class="kw">WITH NOSUPERUSER</span>;
</div>
<div class="code-block">
<span class="lbl">default privileges (future tables)</span>
<span class="kw">ALTER DEFAULT PRIVILEGES IN SCHEMA</span> public<br>
<span class="kw">GRANT SELECT ON TABLES TO</span> readonly;
</div>
</div>
</div>
<!-- transactions — full width -->
<div class="section" id="transactions">
<div class="section-head">
<span class="dot" style="background:#7dd3db"></span>
<h2>transactions</h2>
<a class="back" href="#top">↑</a>
</div>
<div class="code-grid">
<div class="code-block">
<span class="lbl">basic transaction</span>
<span class="kw">BEGIN</span>;<br>
<span class="kw">UPDATE</span> <span class="tbl">accounts</span> <span class="kw">SET</span> balance <span class="op">=</span> balance <span class="op">-</span> <span class="num">100</span> <span class="kw">WHERE</span> id <span class="op">=</span> <span class="num">1</span>;<br>
<span class="kw">UPDATE</span> <span class="tbl">accounts</span> <span class="kw">SET</span> balance <span class="op">=</span> balance <span class="op">+</span> <span class="num">100</span> <span class="kw">WHERE</span> id <span class="op">=</span> <span class="num">2</span>;<br>
<span class="kw">COMMIT</span>; <span class="cmt">-- or ROLLBACK;</span>
</div>
<div class="code-block">
<span class="lbl">savepoints</span>
<span class="kw">SAVEPOINT</span> sp1;<br>
<span class="cmt">-- ... do work ...</span><br>
<span class="kw">ROLLBACK TO</span> sp1; <span class="cmt">-- partial undo</span><br>
<span class="kw">RELEASE SAVEPOINT</span> sp1;
</div>
</div>
<table class="ref-table">
<tr><td><span class="pill p-blue">READ COMMITTED</span></td><td>default — sees committed data at query start</td></tr>
<tr><td><span class="pill p-yellow">REPEATABLE READ</span></td><td>consistent snapshot for whole transaction</td></tr>
<tr><td><span class="pill p-red">SERIALIZABLE</span></td><td>strictest — transactions appear sequential</td></tr>
</table>
</div>
<!-- explain — full width -->
<div class="section" id="explain">
<div class="section-head">
<span class="dot" style="background:#c792ea"></span>
<h2>explain & analyze</h2>
<a class="back" href="#top">↑</a>
</div>
<div class="code-grid">
<div class="code-block">
<span class="lbl">syntax</span>
<span class="kw">EXPLAIN</span> <span class="kw">SELECT</span> * <span class="kw">FROM</span> <span class="tbl">users</span> <span class="kw">WHERE</span> email <span class="op">=</span> <span class="str">'x'</span>;<br>
<span class="kw">EXPLAIN ANALYZE</span> <span class="kw">SELECT</span> ...; <span class="cmt">-- actually executes</span><br>
<span class="kw">EXPLAIN (ANALYZE, BUFFERS, FORMAT JSON)</span> <span class="kw">SELECT</span> ...;
</div>
<div class="code-block">
<span class="lbl">force / disable scan types</span>
<span class="kw">SET</span> enable_seqscan <span class="op">=</span> off; <span class="cmt">-- prefer index scans</span><br>
<span class="kw">SET</span> enable_indexscan <span class="op">=</span> off; <span class="cmt">-- prefer seq scans</span><br>
<span class="kw">RESET</span> enable_seqscan; <span class="cmt">-- restore default</span>
</div>
</div>
<table class="ref-table">
<tr><td>Seq Scan</td><td>full table scan — consider adding an index</td></tr>
<tr><td>Index Scan</td><td>uses index, fetches heap rows</td></tr>
<tr><td>Index Only Scan</td><td>covering index — no heap access needed</td></tr>
<tr><td>Bitmap Heap Scan</td><td>batched index + heap access</td></tr>
<tr><td>Hash Join</td><td>builds hash table — good for large sets</td></tr>
<tr><td>Nested Loop</td><td>good when inner set is small</td></tr>
<tr><td>cost=X..Y</td><td>startup..total estimated cost units</td></tr>
<tr><td>actual time</td><td>real milliseconds — only with ANALYZE</td></tr>
</table>
</div>
<!-- admin queries — full width -->
<div class="section" id="admin">
<div class="section-head">
<span class="dot" style="background:#88cc88"></span>
<h2>handy admin queries</h2>
<a class="back" href="#top">↑</a>
</div>
<div class="code-grid">
<div class="code-block">
<span class="lbl">table sizes</span>
<span class="kw">SELECT</span> relname,<br>
<span class="fn">pg_size_pretty</span>(<span class="fn">pg_total_relation_size</span>(oid))<br>
<span class="kw">FROM</span> pg_class <span class="kw">WHERE</span> relkind <span class="op">=</span> <span class="str">'r'</span><br>
<span class="kw">ORDER BY</span> <span class="fn">pg_total_relation_size</span>(oid) <span class="kw">DESC</span>;
</div>
<div class="code-block">
<span class="lbl">active connections</span>
<span class="kw">SELECT</span> pid, usename, state, query<br>
<span class="kw">FROM</span> pg_stat_activity<br>
<span class="kw">WHERE</span> state <span class="op">!=</span> <span class="str">'idle'</span>;
</div>
<div class="code-block">
<span class="lbl">kill a query</span>
<span class="kw">SELECT</span> <span class="fn">pg_cancel_backend</span>(pid); <span class="cmt">-- graceful</span><br>
<span class="kw">SELECT</span> <span class="fn">pg_terminate_backend</span>(pid); <span class="cmt">-- force kill</span>
</div>
<div class="code-block">
<span class="lbl">long running queries</span>
<span class="kw">SELECT</span> pid, <span class="fn">now</span>() <span class="op">-</span> query_start <span class="kw">AS</span> dur, query<br>
<span class="kw">FROM</span> pg_stat_activity<br>
<span class="kw">WHERE</span> state <span class="op">=</span> <span class="str">'active'</span><br>
<span class="kw">ORDER BY</span> dur <span class="kw">DESC</span>;
</div>
<div class="code-block">
<span class="lbl">missing indexes (high seq scans)</span>
<span class="kw">SELECT</span> relname, seq_scan, idx_scan<br>
<span class="kw">FROM</span> pg_stat_user_tables<br>
<span class="kw">WHERE</span> seq_scan <span class="op">></span> idx_scan<br>
<span class="kw">ORDER BY</span> seq_scan <span class="kw">DESC</span>;
</div>
<div class="code-block">
<span class="lbl">unused indexes</span>
<span class="kw">SELECT</span> indexrelname, idx_scan<br>
<span class="kw">FROM</span> pg_stat_user_indexes<br>
<span class="kw">WHERE</span> idx_scan <span class="op">=</span> <span class="num">0</span><br>
<span class="kw">ORDER BY</span> schemaname, relname;
</div>
<div class="code-block">
<span class="lbl">table bloat / vacuum</span>
<span class="kw">VACUUM ANALYZE</span> <span class="tbl">users</span>;<br>
<span class="kw">VACUUM FULL</span> <span class="tbl">users</span>; <span class="cmt">-- exclusive lock, rewrites</span><br>
<span class="kw">SELECT</span> relname, n_dead_tup, last_autovacuum<br>
<span class="kw">FROM</span> pg_stat_user_tables <span class="kw">ORDER BY</span> n_dead_tup <span class="kw">DESC</span>;
</div>
<div class="code-block">
<span class="lbl">duplicate rows</span>
<span class="kw">SELECT</span> email, <span class="fn">count</span>(*)<br>
<span class="kw">FROM</span> <span class="tbl">users</span><br>
<span class="kw">GROUP BY</span> email<br>
<span class="kw">HAVING</span> <span class="fn">count</span>(*) <span class="op">></span> <span class="num">1</span>;
</div>
</div>
</div>
<!-- jsonb — full width -->
<div class="section" id="jsonb">
<div class="section-head">
<span class="dot" style="background:#f0a070"></span>
<h2>jsonb operators</h2>
<a class="back" href="#top">↑</a>
</div>
<div class="split">
<table class="ref-table">
<tr><td><span class="op">-></span> <span class="str">'key'</span></td><td>get value as json</td></tr>
<tr><td><span class="op">->></span> <span class="str">'key'</span></td><td>get value as text</td></tr>
<tr><td><span class="op">#></span> <span class="str">'{a,b}'</span></td><td>nested value as json</td></tr>
<tr><td><span class="op">#>></span> <span class="str">'{a,b}'</span></td><td>nested value as text</td></tr>
<tr><td><span class="op">@></span></td><td>left contains right</td></tr>
<tr><td><span class="op"><@</span></td><td>left contained by right</td></tr>
<tr><td><span class="op">?</span> <span class="str">'key'</span></td><td>key exists?</td></tr>
<tr><td><span class="op">||</span></td><td>concatenate objects</td></tr>
<tr><td><span class="op">-</span> <span class="str">'key'</span></td><td>delete key</td></tr>
</table>
<div class="code-block" style="border-bottom:none">
<span class="lbl">examples</span>
<span class="kw">SELECT</span> data<span class="op">->></span><span class="str">'name'</span> <span class="kw">FROM</span> <span class="tbl">events</span><br>
<span class="kw">WHERE</span> data <span class="op">@></span> <span class="str">'{"type":"login"}'</span>::<span class="typ">jsonb</span>;<br><br>
<span class="kw">SELECT</span> data<span class="op">#>></span><span class="str">'{user,email}'</span> <span class="kw">FROM</span> <span class="tbl">events</span>;<br><br>
<span class="cmt">-- gin index for @> containment:</span><br>
<span class="kw">CREATE INDEX ON</span> <span class="tbl">events</span> <span class="kw">USING</span> gin(data);
</div>
</div>
</div>
<!-- conditional — full width -->
<div class="section" id="conditional">
<div class="section-head">
<span class="dot" style="background:#6fa8e8"></span>
<h2>conditional & casting</h2>
<a class="back" href="#top">↑</a>
</div>
<div class="code-grid">
<div class="code-block">
<span class="lbl">case expression</span>
<span class="kw">CASE</span><br>
<span class="kw">WHEN</span> score <span class="op">>=</span> <span class="num">90</span> <span class="kw">THEN</span> <span class="str">'A'</span><br>
<span class="kw">WHEN</span> score <span class="op">>=</span> <span class="num">70</span> <span class="kw">THEN</span> <span class="str">'B'</span><br>
<span class="kw">ELSE</span> <span class="str">'C'</span><br>
<span class="kw">END</span>
</div>
<div class="code-block">
<span class="lbl">null handling</span>
<span class="fn">coalesce</span>(val, fallback) <span class="cmt">-- first non-null</span><br>
<span class="fn">nullif</span>(a, b) <span class="cmt">-- null if a = b</span><br>
<span class="fn">greatest</span>(a, b, ...) <span class="cmt">-- largest non-null</span><br>
<span class="fn">least</span>(a, b, ...) <span class="cmt">-- smallest non-null</span>
</div>
<div class="code-block">
<span class="lbl">casting</span>
val<span class="op">::</span><span class="typ">integer</span> <span class="cmt">-- pg shorthand</span><br>
<span class="fn">CAST</span>(val <span class="kw">AS</span> <span class="typ">integer</span>) <span class="cmt">-- sql standard</span><br>
<span class="str">'2024-01-01'</span><span class="op">::</span><span class="typ">date</span><br>
<span class="str">'{"a":1}'</span><span class="op">::</span><span class="typ">jsonb</span>
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<span class="lbl">pattern matching</span>
<span class="kw">WHERE</span> name <span class="kw">LIKE</span> <span class="str">'alice%'</span> <span class="cmt">-- case sensitive</span><br>
<span class="kw">WHERE</span> name <span class="kw">ILIKE</span> <span class="str">'alice%'</span> <span class="cmt">-- case insensitive</span><br>
<span class="kw">WHERE</span> name <span class="op">~</span> <span class="str">'^alice'</span> <span class="cmt">-- regex</span><br>
<span class="kw">WHERE</span> name <span class="op">~*</span> <span class="str">'^alice'</span> <span class="cmt">-- regex, no case</span>
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