mysql> alter table t1 -> alter check t1_chk_1 not enforced; Query OK, 0 rows affected (0.02 sec) Records: 0 Duplicates: 0 Warnings: 0 mysql> show create table t1\G *** 1. row *** Table: t1 Create Table: CREATE TABLE `t1` ( `c1` int DEFAULT NULL, `c2` int DEFAULT NULL, ...
MySQL> alter table t1 add i int; Query OK, 0 rows affected (0.41 sec) Records: 0 Duplicates: 0 Warnings: 0 #然后再次执行sp,就会发现这次执行了这句SQL的prepare再进行execute。 MySQL> call p1; Query OK, 0 rows affected (34.24 sec)
MySQL> call p1; #这里第二次操作,直接执行update这句SQL的execute。 Query OK, 0 rows affected (13.78 sec)#接着我们执行表结构的更新。 MySQL> alter table t1 add i int; Query OK, 0 rows affected (0.41 sec) Records: 0 Duplicates: 0 Warnings: 0#然后再次执行sp,就会发现这次执行了这句SQL的pr...
MySQL>altertablet1 add iint;Query OK,0rows affected(0.41sec)Records:0Duplicates:0Warnings:0#然后再次执行sp,就会发现这次执行了这句SQL的prepare再进行execute。 MySQL>call p1;Query OK,0rows affected(34.24sec) 1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 1...
table: b type: ref possible_keys: ind_company_id key: ind_company_id key_len: 5 ref: sakila.a.company_id rows: 1 Extra: Usingwhere; Usingindex 2rowsinset(0.00 sec) 每个列的简单解释如下: select_type:表示 SELECT 的类型,常见的取值有 SIMPLE(简单表,即不使用表连接或者子查询)、PRIMARY(主...
我们常见的数据库都实现了检查约束,例如 Oracle、SQL Server、PostgreSQL 以及 SQLite;然而 MySQL 一直以来没有真正实现该功能,直到最新的 MySQL 8.0.16。 MySQL 8.0.15 之前 在MySQL 8.0.15 以及之前的版本中,虽然 CREATE TABLE 语句允许CHECK (expr)形式的检查约束语法,但实际上解析之后会忽略该子句。例如 ...
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你也可以通过alter table的方式增加或删除约束: root@test10:45:08>ALTER TABLE t1 ADD CONSTRAINT check ((c1 + c2 + c3) >1000);QueryOK,0rows affected (0.02sec)Records:0Duplicates:0Warnings:0root@test10:45:39>INSERT INTO t1 values (1999,50,90);QueryOK,1row affected (0.00sec)root@test10...
One reason it can work on very large tables is that it divides each table into chunks of rows, and checksums each chunk with a single REPLACE..SELECT query. It varies the chunk size to make the checksum queries run in the desired amount of time. The goal of chunking the tables, instead...
in set (0.00 sec) mysql> create table B (id int, name varchar(20)); Query OK, 0 rows affected (0.02 sec) -- A与B表数据类型顺序对应,不需调整 mysql> insert into B select * from A; Query OK, 5 rows affected (0.01 sec) Records: 5 Duplicates: 0 Warnings: 0 mysql> select * ...