mysql的on和in用法_数据库中in、on、with的用法及示例。
with用法:
創建一個表:
create table regr (pid integer,id integer, name char(20))
alter table regr alter id set not null add primary key(id)
insert into regr values(-1,1,'library'),(1,2,'news'),(2,3,'world news'),(2,4,'politics'),(2,5,'bussiness')
(2,6,'science'),(2,7,'technology'),(1,8,'sports'),(8,9,'local'),(8,10,'collegiate'),(8,11,'professional')
(9,12,'soccer'),(10,13,'soccer'),(11,14,'soccer'),(9,15,'football'),(10,16,'football'),(11,17,'football'
使用with得到數據樹
WITH RPL (PID, ID, name) AS
(SELECT ROOT.PID, ROOT.ID, ROOT.NameFROM regr ROOT
WHERE ROOT.PID = 8
UNION ALL
SELECT CHILD.PID, CHILD.ID, CHILD.Name
FROM RPL PARENT, regr CHILD
WHERE PARENT.ID = CHILD.PID)
SELECT DISTINCT PID, ID, Name
FROM RPL
ORDER BY PID, ID, Name
總結
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