How do you use the "WITH" clause in MySQL?
MySQL prior to version 8.0 doesn't support the WITH clause (CTE in SQL Server parlance; Subquery Factoring in Oracle), so you are left with using:
- TEMPORARY tables
- DERIVED tables
- inline views (effectively what the WITH clause represents - they are interchangeable)
The request for the feature dates back to 2006.
As mentioned, you provided a poor example - there's no need to perform a subselect if you aren't altering the output of the columns in any way:
SELECT *
FROM ARTICLE t
JOIN USERINFO ui ON ui.user_userid = t.article_ownerid
JOIN CATEGORY c ON c.catid = t.article_categoryid
WHERE t.published_ind = 0
ORDER BY t.article_date DESC
LIMIT 1, 3
Here's a better example:
SELECT t.name,
t.num
FROM TABLE t
JOIN (SELECT c.id
COUNT(*) 'num'
FROM TABLE c
WHERE c.column = 'a'
GROUP BY c.id) ta ON ta.id = t.id
Mysql Developers Team announced that version 8.0 will have Common Table Expressions in MySQL (CTEs). So it will be possible to write queries like this:
WITH RECURSIVE my_cte AS
(
SELECT 1 AS n
UNION ALL
SELECT 1+n FROM my_cte WHERE n<10
)
SELECT * FROM my_cte;
+------+
| n |
+------+
| 1 |
| 2 |
| 3 |
| 4 |
| 5 |
| 6 |
| 7 |
| 8 |
| 9 |
| 10 |
+------+
10 rows in set (0,00 sec)