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 in most popular RDBMSs and be as short as possible and refference to
 a reliable source for more info. You can set up your environment and import sample data in the
 <a href=./posts/setup>Setup</a> post. If you find any issues or want to add more examples,
-feel free to open an issue or send a pull request in <a href=https://github.com/peymanslh/sql>GitHub</a>.</p></div></div><h2>Introduction <span class=dot></span></h2><ul class=home-posts><li><a href=./posts/setup/>Setup</a></li><li><a href=./posts/sample-database-structure/>Sample Database Structure</a></li><li><a href=./posts/comment/>Comment</a></li></ul><h2>Database and Table Management<span class=dot></span></h2><ul class=home-posts><li><a href=./posts/create-and-drop-database/>Create and Drop Database</a></li><li><a href=./posts/create-and-drop-table/>Create and Drop Table</a></li></ul><h2>Modifying Data<span class=dot></span></h2><ul class=home-posts><li><a href=./posts/insert/>INSERT</a></li><li><a href=./posts/update/>UPDATE</a></li><li><a href=./posts/delete/>DELETE</a></li></ul><h2>Query and Filtering Data<span class=dot></span></h2><ul class=home-posts><li><a href=./posts/select/>SELECT</a></li><li><a href=./posts/where/>WHERE</a></li><li><a href=./posts/order-by/>ORDER BY</a></li><li><a href=./posts/group-by/>GROUP BY</a></li><li><a href=./posts/and-or-not/>AND, OR, NOT</a></li><li><a href=./posts/limit/>LIMIT</a></li><li><a href=./posts/min-max/>MIN, MAX</a></li></ul><h2>Latest Posts<span class=dot></span></h2><ul class=home-posts><li><a href=./posts/min-max/>MIN, MAX</a></li><li><a href=./posts/comment/>Comment</a></li><li><a href=./posts/limit/>LIMIT</a></li><li><a href=./posts/and-or-not/>AND, OR, NOT</a></li><li><a href=./posts/group-by/>GROUP BY</a></li><li><a href=./posts/order-by/>ORDER BY</a></li><li><a href=./posts/delete/>DELETE</a></li><li><a href=./posts/update/>UPDATE</a></li><li><a href=./posts/insert/>INSERT</a></li><li><a href=./posts/where/>WHERE</a></li><li><a href=./posts/select/>SELECT</a></li><li><a href=./posts/create-and-drop-table/>Create and Drop Table</a></li><li><a href=./posts/create-and-drop-database/>Create and Drop Database</a></li><li><a href=./posts/sample-database-structure/>Sample Database Structure</a></li><li><a href=./posts/setup/>Setup</a></li></ul><div class=footer><div class=footer-copy>© 2024 SQL by example.</div><div class=footer-social><span class="social-icon social-icon-github"><a href=https://github.com/peymanslh/sql title=github target=_blank rel=noopener><img src=./images/social/github.svg width=24 height=24 alt=github></a></span></div></div></div><script type=text/javascript src=./js/bundle.min.1ff4c3efa6718e4b48bf69ba81bb9b232f6f3e1407b7ea6ce8e5a6fdaed5af56.js></script></body></html>
+feel free to open an issue or send a pull request in <a href=https://github.com/peymanslh/sql>GitHub</a>.</p></div></div><h2>Introduction <span class=dot></span></h2><ul class=home-posts><li><a href=./posts/setup/>Setup</a></li><li><a href=./posts/sample-database-structure/>Sample Database Structure</a></li></ul><h2>Database and Table Management<span class=dot></span></h2><ul class=home-posts><li><a href=./posts/create-and-drop-database/>Create and Drop Database</a></li><li><a href=./posts/create-and-drop-table/>Create and Drop Table</a></li></ul><h2>Modifying Data<span class=dot></span></h2><ul class=home-posts><li><a href=./posts/insert/>INSERT</a></li><li><a href=./posts/update/>UPDATE</a></li><li><a href=./posts/delete/>DELETE</a></li></ul><h2>Query and Filtering Data<span class=dot></span></h2><ul class=home-posts><li><a href=./posts/select/>SELECT</a></li><li><a href=./posts/where/>WHERE</a></li><li><a href=./posts/order-by/>ORDER BY</a></li><li><a href=./posts/group-by/>GROUP BY</a></li><li><a href=./posts/and-or-not/>AND, OR, NOT</a></li><li><a href=./posts/limit/>LIMIT</a></li><li><a href=./posts/comment/>Comment</a></li><li><a href=./posts/min-max/>MIN, MAX</a></li><li><a href=./posts/count-sum-avg/>COUNT, SUM, AVG</a></li><li><a href=./posts/as/>AS</a></li><li><a href=./posts/like/>LIKE</a></li></ul><div class=footer><div class=footer-copy>© 2024 SQL by example.</div><div class=footer-social><span class="social-icon social-icon-github"><a href=https://github.com/peymanslh/sql title=github target=_blank rel=noopener><img src=./images/social/github.svg width=24 height=24 alt=github></a></span></div></div></div><script type=text/javascript src=./js/bundle.min.1ff4c3efa6718e4b48bf69ba81bb9b232f6f3e1407b7ea6ce8e5a6fdaed5af56.js></script></body></html>

index.xml

@@ -1,4 +1,8 @@
-<?xml version="1.0" encoding="utf-8" standalone="yes"?><rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>Learn SQL by example on SQL by example</title><link>https://peyman.blog/sql/</link><description>Recent content in Learn SQL by example on SQL by example</description><generator>Hugo -- gohugo.io</generator><language>en-us</language><managingEditor>[email protected] (Peyman Salehi)</managingEditor><webMaster>[email protected] (Peyman Salehi)</webMaster><lastBuildDate>Sat, 03 Feb 2024 15:49:57 +0330</lastBuildDate><atom:link href="https://peyman.blog/sql/index.xml" rel="self" type="application/rss+xml"/><item><title>MIN, MAX</title><link>https://peyman.blog/sql/posts/min-max/</link><pubDate>Sat, 03 Feb 2024 15:49:57 +0330</pubDate><author>[email protected] (Peyman Salehi)</author><guid>https://peyman.blog/sql/posts/min-max/</guid><description>MIN returns the smallest value of a column. MAX returns the biggest value of a column.
+<?xml version="1.0" encoding="utf-8" standalone="yes"?><rss version="2.0" xmlns:atom="http://www.w3.org/2005/Atom"><channel><title>Learn SQL by example on SQL by example</title><link>https://peyman.blog/sql/</link><description>Recent content in Learn SQL by example on SQL by example</description><generator>Hugo -- gohugo.io</generator><language>en-us</language><managingEditor>[email protected] (Peyman Salehi)</managingEditor><webMaster>[email protected] (Peyman Salehi)</webMaster><lastBuildDate>Mon, 05 Feb 2024 11:17:10 +0330</lastBuildDate><atom:link href="https://peyman.blog/sql/index.xml" rel="self" type="application/rss+xml"/><item><title>LIKE</title><link>https://peyman.blog/sql/posts/like/</link><pubDate>Mon, 05 Feb 2024 11:17:10 +0330</pubDate><author>[email protected] (Peyman Salehi)</author><guid>https://peyman.blog/sql/posts/like/</guid><description>LIKE is use in WHERE condition to find data based on a pattern.
+There are two wildcards that we can use with LIKE:
+%: represents zero, one, or multiple characters _: represents one, single character. -- find all users with first_name of John SELECT id, first_name, last_name FROM users WHERE first_name LIKE &amp;#39;John&amp;#39;; -- +-----+------------+-----------+ -- | id | first_name | last_name | -- |-----+------------+-----------| -- | 14 | John | Combs | -- | 51 | John | Fritz | -- | 285 | John | Sanders | -- | 445 | John | Wise | -- | 485 | John | Peterson | -- | 501 | John | Moreno | -- | 502 | John | Moreno | -- +-----+------------+-----------+ -- find all users that their first_name starts with A SELECT id, first_name, last_name FROM users WHERE first_name LIKE &amp;#39;A%&amp;#39;; -- +-----+------------+-----------+ -- | id | first_name | last_name | -- |-----+------------+-----------| -- | 13 | Andrew | Mercado | -- | 42 | Adrian | Ewing | -- | 74 | Audrey | Edwards | -- find all users that their first_name ends with n SELECT id, first_name, last_name FROM users WHERE first_name LIKE &amp;#39;%n&amp;#39;; -- +-----+------------+-----------+ -- | id | first_name | last_name | -- |-----+------------+-----------| -- | 1 | Carmen | Malone | -- | 3 | Brandon | Jenkins | -- | 7 | Jocelyn | Williams | -- | 10 | Steven | Perez | -- .</description></item><item><title>AS</title><link>https://peyman.blog/sql/posts/as/</link><pubDate>Mon, 05 Feb 2024 11:01:38 +0330</pubDate><author>[email protected] (Peyman Salehi)</author><guid>https://peyman.blog/sql/posts/as/</guid><description>AS keyword is use to make an alias for a column name.
+SELECT COUNT(id), AVG(total_price), user_id FROM orders GROUP BY user_id; -- V V -- +-------+-----------------------+---------+ -- | count | avg | user_id | -- |-------+-----------------------+---------| -- | 1 | 2220.0000000000000000 | 384 | -- | 3 | 1319.3333333333333333 | 351 | -- Use alias for count and avg columns SELECT COUNT(id) as number_of_orders, AVG(total_price) avg_total_price, user_id FROM orders GROUP BY user_id; -- V V -- +------------------+-----------------------+---------+ -- | number_of_orders | avg_total_price | user_id | -- |------------------+-----------------------+---------| -- | 1 | 2220.</description></item><item><title>COUNT, SUM, AVG</title><link>https://peyman.blog/sql/posts/count-sum-avg/</link><pubDate>Sun, 04 Feb 2024 13:45:07 +0330</pubDate><author>[email protected] (Peyman Salehi)</author><guid>https://peyman.blog/sql/posts/count-sum-avg/</guid><description>COUNT returns the number of rows for a column.
+-- return the number of all users SELECT COUNT(*) FROM users; -- +-------+ -- | count | -- |-------| -- | 502 | -- +-------+ -- find the number of orders by each user SELECT COUNT(*), user_id FROM orders GROUP BY user_id ORDER BY user_id; -- +-------+---------+ -- | count | user_id | -- |-------+---------| -- | 2 | 1 | -- | 1 | 2 | -- | 3 | 3 | -- | 4 | 4 | -- .</description></item><item><title>MIN, MAX</title><link>https://peyman.blog/sql/posts/min-max/</link><pubDate>Sat, 03 Feb 2024 15:49:57 +0330</pubDate><author>[email protected] (Peyman Salehi)</author><guid>https://peyman.blog/sql/posts/min-max/</guid><description>MIN returns the smallest value of a column. MAX returns the biggest value of a column.
 -- return the lowest total_price from orders of user with id of 10 SELECT MIN(total_price) FROM orders WHERE user_id = 10; -- +------+ -- | min | -- |------| -- | 1132 | -- +------+ -- return the highest total_price from the orders of user with id of 10 SELECT MAX(total_price) FROM orders WHERE user_id = 10; -- +------+ -- | max | -- |------| -- | 1998 | -- +------+ PostgreSQL docs</description></item><item><title>Comment</title><link>https://peyman.blog/sql/posts/comment/</link><pubDate>Sat, 03 Feb 2024 15:11:15 +0330</pubDate><author>[email protected] (Peyman Salehi)</author><guid>https://peyman.blog/sql/posts/comment/</guid><description>When you writing multiline SQL queries you can use -- to comment a single line and use /* */ to comment multiline texts.
 -- Single line comment /* Multi line comment */</description></item><item><title>LIMIT</title><link>https://peyman.blog/sql/posts/limit/</link><pubDate>Fri, 02 Feb 2024 15:09:44 +0330</pubDate><author>[email protected] (Peyman Salehi)</author><guid>https://peyman.blog/sql/posts/limit/</guid><description>When the number of rows in a select query are a lot, we can limit them by the LIMIT statement.
 -- only return 3 item SELECT * FROM users LIMIT 3; -- +----+---------------------+------------+-----------+--------------------------------+----------------+--------+ -- | id | datetime_joined | first_name | last_name | email | city | active | -- |----+---------------------+------------+-----------+--------------------------------+----------------+--------| -- | 1 | 2023-08-18 21:44:13 | Carmen | Malone | [email protected] | East Jeanmouth | True | -- | 2 | 2023-07-27 04:31:11 | Stephanie | Wallace | hjennings@curry.</description></item><item><title>AND, OR, NOT</title><link>https://peyman.blog/sql/posts/and-or-not/</link><pubDate>Fri, 02 Feb 2024 14:18:01 +0330</pubDate><author>[email protected] (Peyman Salehi)</author><guid>https://peyman.blog/sql/posts/and-or-not/</guid><description>With the help of AND, OR, and NOT we can add more power to our query conditions.

posts/as/index.html

@@ -0,0 +1,27 @@
+<!doctype html><html lang=en><head><meta charset=utf-8><meta http-equiv=x-ua-compatible content="ie=edge"><title>AS - SQL by example</title><meta name=viewport content="width=device-width,initial-scale=1"><link rel=icon href=https://peyman.blog/sql/favicon.png><link rel=alternate type=application/rss+xml href=https://peyman.blog/sql/index.xml title="SQL by example"><link rel=stylesheet href=../../css/style.min.b7a8f934af918fc60a41bae619210b3560306dbdbba86726567d6993bc1bc64c.css><meta property="og:title" content="AS"><meta property="og:type" content="website"><meta property="og:url" content="https://peyman.blog/sql/posts/as/"><meta name=twitter:card content="summary"><meta name=twitter:site content="@_peymanslh"><meta name=twitter:creator content="@_peymanslh"><link rel=preconnect href=https://fonts.googleapis.com><link rel=preconnect href=https://fonts.gstatic.com crossorigin><link href="https://fonts.googleapis.com/css2?family=IBM+Plex+Mono:ital,wght@0,500;0,700;1,500&family=Libre+Caslon+Text:wght@700&family=Pridi:wght@300;400;600;700&display=swap" rel=stylesheet></head><body class="page page-blog-single"><div id=wrapper class=wrapper><div class=header><a class=header-logo href=https://peyman.blog/sql/>SQL by example</a><div class=menu-main><ul><li class=menu-item-about><a href=../../pages/about/>About</a></li><li class=menu-item-posts><a href=../../posts/>Posts</a></li></ul></div></div><div class=blog><div class=intro><h1>AS<span class=dot></span></h1><ul class=post-tags><li><a href=https://peyman.blog/sql/tags/query/>query</a></li><li><a href=https://peyman.blog/sql/tags/postgresql/>postgresql</a></li></ul></div><div class=content><p><code>AS</code> keyword is use to make an alias for a column name.</p><div class=highlight><pre style=color:#d8dee9;background-color:#2e3440;-moz-tab-size:4;-o-tab-size:4;tab-size:4><code class=language-sql data-lang=sql><span style=color:#81a1c1;font-weight:700>SELECT</span>
+  <span style=color:#81a1c1;font-weight:700>COUNT</span><span style=color:#eceff4>(</span>id<span style=color:#eceff4>),</span>
+  <span style=color:#81a1c1;font-weight:700>AVG</span><span style=color:#eceff4>(</span>total_price<span style=color:#eceff4>),</span>
+  user_id
+<span style=color:#81a1c1;font-weight:700>FROM</span> orders
+<span style=color:#81a1c1;font-weight:700>GROUP</span> <span style=color:#81a1c1;font-weight:700>BY</span> user_id<span style=color:#eceff4>;</span>
+<span style=color:#616e87;font-style:italic>--     V      V
+</span><span style=color:#616e87;font-style:italic>-- +-------+-----------------------+---------+
+</span><span style=color:#616e87;font-style:italic>-- | count | avg                   | user_id |
+</span><span style=color:#616e87;font-style:italic>-- |-------+-----------------------+---------|
+</span><span style=color:#616e87;font-style:italic>-- | 1     | 2220.0000000000000000 | 384     |
+</span><span style=color:#616e87;font-style:italic>-- | 3     | 1319.3333333333333333 | 351     |
+</span><span style=color:#616e87;font-style:italic></span>
+<span style=color:#616e87;font-style:italic>-- Use alias for count and avg columns
+</span><span style=color:#616e87;font-style:italic></span><span style=color:#81a1c1;font-weight:700>SELECT</span>
+  <span style=color:#81a1c1;font-weight:700>COUNT</span><span style=color:#eceff4>(</span>id<span style=color:#eceff4>)</span> <span style=color:#81a1c1;font-weight:700>as</span> number_of_orders<span style=color:#eceff4>,</span>
+  <span style=color:#81a1c1;font-weight:700>AVG</span><span style=color:#eceff4>(</span>total_price<span style=color:#eceff4>)</span> avg_total_price<span style=color:#eceff4>,</span>
+  user_id
+<span style=color:#81a1c1;font-weight:700>FROM</span> orders
+<span style=color:#81a1c1;font-weight:700>GROUP</span> <span style=color:#81a1c1;font-weight:700>BY</span> user_id<span style=color:#eceff4>;</span>
+<span style=color:#616e87;font-style:italic>--          V                 V
+</span><span style=color:#616e87;font-style:italic>-- +------------------+-----------------------+---------+
+</span><span style=color:#616e87;font-style:italic>-- | number_of_orders | avg_total_price       | user_id |
+</span><span style=color:#616e87;font-style:italic>-- |------------------+-----------------------+---------|
+</span><span style=color:#616e87;font-style:italic>-- | 1                | 2220.0000000000000000 | 384     |
+</span><span style=color:#616e87;font-style:italic>-- | 3                | 1319.3333333333333333 | 351     |
+</span></code></pre></div></div></div><div class=footer><div class=footer-copy>© 2024 SQL by example.</div><div class=footer-social><span class="social-icon social-icon-github"><a href=https://github.com/peymanslh/sql title=github target=_blank rel=noopener><img src=../../images/social/github.svg width=24 height=24 alt=github></a></span></div></div></div><script type=text/javascript src=../../js/bundle.min.1ff4c3efa6718e4b48bf69ba81bb9b232f6f3e1407b7ea6ce8e5a6fdaed5af56.js></script></body></html>