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Detailed explanation and usage of with function in SQL

2022-04-23 13:40:00 【Wangcai 2】

WITH AS The phrase , Also called subquery part , Define a SQL After fragment , The SQL Fragments can be used by the whole SQL The statement uses . sometimes ,with as To improve SQL The readability of statements , Reduce nesting redundancy .

In a standard database , Such as hive,Oracle,DB2,SQL SERVER,PostgreSQL All support. WITH AS Statement for recursive query . Only MySQL Is not supported .

with A as
(select distinct(sno),sname,ssex,sclass from student),
B as
(select sno,cno,degree from score )

-- Use the above defined A,B
select * from A,B
where A.sno =B.sno

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