3 rows in set (0.00 sec) 在使用distinct指定多个字段时,只有被指定的这些字段的值都相同,才会被认为是重复的 7、在查询具有一类相同特征的数据时,需要用到模糊查询,这是就需要使用like关键字select 查询内容 from 表名 where 内容 (not) like ‘匹配的字符串’ 百分号通配符%:表示匹配任意长度的任意字符串 se...
runoobdb# select * from COMPANY;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|850006|Kim|22|South-Hall|450007|James|24|Houston|10000(7rows) 以下SQL 语句将删除 ID 为 2...
# 插入数据INSERTINTOuser_tbl(name, signup_date)VALUES('张三','2013-12-22'); # 选择记录SELECT*FROMuser_tbl; # 更新数据UPDATEuser_tblsetname='李四'WHEREname='张三'; # 删除记录DELETEFROMuser_tblWHEREname='李四'; # 添加栏位ALTERTABLEuser_tblADDemailVARCHAR(40); # 更新结构ALTERTABLEuser_t...
1 testdb=# DELETE FROM t1 WHERE id = 1;2 DELETE 13 testdb=# DELETE FROM t1 WHERE id = 2;4 DELETE 156 testdb=# SELECT lp as tuple, t_xmin, t_xmax, t_field3 as t_cid, t_ctid,t_data FROM heap_page_items(get_raw_p...
一、查询基础 1、连接数据库 C:\PostgreSQL\9.5\bin\psql.exe -U postgres -d shop 2、检查数据库连接是否成功 SELECT 1; 3、创建数据库 CREATE DATABASE shop; 4、退出数据库口令 \q 5、\d 数据库 ——得到所有表的
FOR the_count IN EXECUTE ''SELECT COUNT(*) AS "count" FROM '' || t_name.relname LOOP END LOOP; -- 存储表名 r.table_name := t_name.relname; -- 存储行数 r.num_rows := the_count.count; -- 如果当前我们传入的是一个大于0的,则认为需要执行清除操作。 IF limitNum>0 THEN -- ...
DELETE 1 Which means that1row was deleted. Display Table To check the result we can display the table with this SQL statement: Example SELECT * FROM cars; Run Example » Delete All Records It is possible to delete all rows in a table without deleting the table. This means that the tab...
DELETE 1 //seesion2: testdb=# select ctid, xmin, xmax, cmin, cmax, oid, id from t1; ctid | xmin | xmax | cmin | cmax | oid | id ---+---+---+---+---+---+--- (0,1) | 80853357 | 80853360 | 0 | 0 | 17569 | 1 (0,2) | 80853358 | 80853360 | 1 | 1 ...
DELETE FROM table_name WHERE condition LIMIT number_of_rows; 如果你只想删除前面提到的employees表中的前10个薪水低于3000的员工,你可以这样写: DELETE FROM employees WHERE salary < 3000 LIMIT 10; 使用分区表删除数据 如果你的表非常大,删除操作可能会非常耗时,在这种情况下,一种有效的策略是使用分区表,分...
Command: SELECT Description: retrieve rows from a table or view Syntax: [ WITH [ RECURSIVE ] with_query [, ...] ] SELECT [ ALL | DISTINCT [ ON ( expression [, ...] ) ] ] [ * | expression [ [ AS ] output_name ] [, ...] ] [ FROM from_item [, ...] ] [ WHERE condi...