SELECT l.* FROM t_left l WHERE NOT EXISTS ( SELECT NULL FROM t_right r WHERE r.value = l.value ); 我们先把环境准备一下: postgres 11.9 1 2 3 4 5 6 7 8 9 10 CREATE TABLE t_left ( id INT NOT NULL PRIMARY KEY, value INT NOT NULL, stuffing VARCHAR(200) NOT NULL ); CREATE...
NOT EXISTS postgres=# SELECT l.id, l.valuepostgres-# FROM t_left lpostgres-# WHERE NOT EXISTSpostgres-# (postgres(# SELECT selectpostgres(# FROM t_right rpostgres(# WHERE r.value = l.valuepostgres(# );id|value---+---10000|030000|020000|040000|060000|050000|080000|070000|090000|010000...
NAME FROM A WHERE EXISTS(SELECT * FROM B WHERE A.I
查看某个库中某个表的记录...\dt 列出表名 SELECT tablename FROM pg_tables; WHERE tablename NOT LIKE 'pg%' AND tablename NOT LIKE...'sql_%' ORDER BY tablename; 列出数据库名 \l 或 SELECT datname FROM pg_database; 切换数据库 \c 数据库名 1、通过命令行查询...\d 数据库 —...
postgresql中,许多ddl语句支持if exists、if not exists。例如: 1 2 3 4 5 postgres=#createtableifnotexists abce(); CREATETABLE postgres=#droptableif exists abce; DROPTABLE postgres=# 建议只是在必须的时候在ddl中使用if exists、if not exists。以下是三个示例,展示了过度使用他们而产生的负面效应。
查询customer表,且customer.customer_id不在(payment表中的且是payment表中amount>11的那些customer_id)selectcustomer_id,first_name,last_namefromcustomerwherenot exists(selectnullfrompaymentwherecustomer.customer_id=payment.customer_id and amount>11);【注】:NOTIN的效率非常低,如果可以的话建议使用NOTEXISTS。
select pay_z.amount,pay_z.staff_id from payment as pay_z where not exists (select * from rental as ren where pay_z.rental_id = ren.rental_id and rental_date > '2000-09-08' and pay_z.staff_id = 1)) as pay on pay.staff_id = sta.staff_id ...
PostgreSQL的EXISTS用法可以用于检查子查询中是否存在结果。它返回一个布尔值,如果子查询返回至少一个行,则为true;否则为false。 以下是EXISTS用法的示例: 1.检查子查询中是否存在结果: SELECT column_name FROM table_name WHERE EXISTS (SELECT column_name FROM other_table WHERE condition); 2.结合EXISTS和NOT操...
aNOTa TRUEFALSE FALSETRUE NULLNULL 实例 创建COMPANY 表(下载 COMPANY SQL 文件),数据内容如下: runoobdb=#select*fromCOMPANY;id|name|age|address|salary---+---+---+---+---1|Paul|32|California|200002|Allen|25|Texas|150003|Teddy|23|Norway|200004|Mark|25|Rich-Mond|650005|David|27|Texas...
select id from users where preferred_language = 'zh_CN' and private_profile = True ) as temp; 大小写 PostgreSQL是区分大小写的,这对于Windows下用户习惯SQL Serve的人来说可能有点别扭。 对策: 如果"小写化"或"大写化"数据,比较费劲,在将数据加入查询中之前,先查看字段的形式。 如果在join时候需求,请...