Question

有没有办法将查询应用于mysql数据库中的每个表？

像

这样的东西

SELECT count(*) FROM {ALL TABLES}
-- gives the number of count(*) in each Table

和

DELETE FROM {ALL TABLES}
-- Like DELETE FROM TABLE applied on each Table

Answer 1

select sum(table_rows) as total_rows
from information_schema.tables
where table_schema = 'your_db_name'

注意这只是一个近似值

为了删除所有表格的内容，你可以做类似的事情

select concat('truncate ',table_name,';')
from information_schema.tables
where table_schema = 'your_db_name'

然后运行此查询的输出。

<强>更新

这是将truncate table应用于特定数据库中所有表的存储过程

delimiter //
drop procedure if exists delete_contents //
create procedure delete_contents (in db_name varchar(100))
begin
declare finish int default 0;
declare tab varchar(100);
declare cur_tables cursor for select table_name from information_schema.tables where table_schema = db_name and table_type = 'base table';
declare continue handler for not found set finish = 1;
open cur_tables;
my_loop:loop
fetch cur_tables into tab;
if finish = 1 then
leave my_loop;
end if;

set @str = concat('truncate ', tab);
prepare stmt from @str;
execute stmt;
deallocate prepare stmt;
end loop;
close cur_tables;
end; //
delimiter ;

call delete_contents('your_db_name');

Answer 2

如果表格与任何字段相关，则可以使用

等表格的别名

select count(*) from table1 tb1, table2 tb2, table3 tb3 where
tb1.field1 = tb2.field2 and tb2.field2 = tb3.field3

与之相似，

delete from table1 tb1, table2 tb2, table3 tb3 where
tb1.field1 = tb2.field2 and tb2.field2 = tb3.field3

您可以根据自己的要求提供条件。

如果表格没有关系，请使用下面的

SELECT
  (SELECT COUNT(*) FROM table1 WHERE someCondition) as count1, 
  (SELECT COUNT(*) FROM table2 WHERE someCondition) as count2,
  (SELECT COUNT(*) FROM table3 WHERE someCondition) as count3

如果没有条件，您可以删除where子句。

输出：

| count1 | count2 |共3个记录|

| 50 | 36 | 21 |

将mysql查询应用于数据库中的每个表

2 个答案: