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SQL - Revision history
2026-05-09T08:08:26Z
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Kenneth: /* Subqueries */
2018-11-28T20:57:46Z
<p><span dir="auto"><span class="autocomment">Subqueries</span></span></p>
<p><b>New page</b></p><div>== Subqueries ==<br />
<br />
SELECT * FROM t1 WHERE column1 = (SELECT column1 FROM t2);<br />
<br />
Subquery Converted to Inner Join:<br />
# Subquery:<br />
SELECT name <br />
FROM animal <br />
WHERE id <br />
IN (SELECT animal_id FROM animal_food);<br />
<br />
# Inner Join:<br />
SELECT DISTINCT name <br />
FROM animal,animal_food <br />
WHERE animal.id=animal_id;<br />
<br />
Subquery Converted to Outer Join:<br />
# Subquery:<br />
SELECT name FROM animal WHERE id NOT IN (SELECT animal_id FROM animal_food);<br />
<br />
# Outer Join:<br />
SELECT name FROM animal LEFT JOIN animal_food ON animal.id=animal_id WHERE animal_id IS NULL;<br />
<br />
<br />
<br />
<br />
a.k.a. Inner Select<br />
<br />
*[http://dev.mysql.com/doc/refman/5.0/en/subqueries.html MySQL :: MySQL 5.0 Reference Manual :: 12.2.9 Subquery Syntax]<br />
*[http://www.databasejournal.com/features/mysql/article.php/3434641/MySQL-Subqueries.htm MySQL Subqueries]<br />
<br />
== Insert ==<br />
<br />
<br />
INSERT INTO table_name (column1, column2, column3, ...)<br />
VALUES (value1, value2, value3, ...);<br />
<br />
INSERT INTO table_name<br />
VALUES (value1, value2, value3, ...);<br />
<br />
ref: https://www.w3schools.com/sql/sql_insert.asp<br />
<br />
== Replace Text ==<br />
<br />
UPDATE `knowledgebase`.`kbentry` SET description=REPLACE(description, '/console/', '/edit/');<br />
<br />
# REPLACE(string, old_string, new_string)<br />
SELECT REPLACE(MAC, '-', ':') from HOSTS;<br />
<br />
ref: https://www.w3schools.com/sql/func_sqlserver_replace.asp</div>
Kenneth