MySQL字段允许为空alter mysql建表允许为空,建表的完整性约束:notnull与defaultuniqueprimaryauto_incrementforeignkey外键的变种 三种关系一、介绍约束条件与数据类型的宽度一样,都是可选参数作用:用于保证数据的完整性和一致性主要分为:PRIMARYKEY(PK)#标识该字
mysql> alter table user2 add foreign key(pid) references provinces(id); 添加/删除默认约束 alter table 表名 alter [column] col_name {set default literal | drop default} 例: mysql> alter table user2 add age tinyint unsigned not null; mysql> alter table user2 alter age set default 15; ...
tables, sql_mode=ANSI,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTIONHow to repeat:CREATE TABLE "ttt" ( "a" int(11), "b" int(11) NOT NULL ); # Behaves according to Quote 1 - MySQL forced a default value of...
In fact the default value for the enum UCS2 values turns out to be corrupted that can can be seen from the following output: mysql> SHOW CREATE TABLE test; +---+---
If there is a conflict between the old_alter_table setting and an ALGORITHM clause with a value other than DEFAULT, the ALGORITHM clause takes precedence. For InnoDB tables, an ALTER TABLE operation that uses the COPY algorithm on a table that resides in a shared tablespace can increase the...
As of MySQL 8.0.16, specifying an ENCRYPTION clause with a value other than 'N' or '' is not permitted if the table uses a storage engine that does not support encryption. Previously, the clause was accepted. Attempting to create a table without an ENCRYPTION clause in an encryption-enable...
1. drop：删除数据库 drop语句将表所占用的空间全释放掉。drop > truncate > delete 方式1：如果要...
MySQL Forums Forum List»Stored Procedures Advanced Search New Topic Procedure for "mass" table alter Posted by:ghaith hachem Date: August 25, 2008 06:21AM Hey, i need to add a default value to all int and double fields in a certain table, so i thought of having a stored procedure ...
本文主要介绍 MySQL 模式中暂不支持的 DDL 语法。 样例表: MySQL [test]> CREATE TABLE `t1` (`id` varchar(64) DEFAULT NULL); Query OK, 0 rows affected (0.064 sec) 暂不支持缩短字段的长度。 MySQL [test]> alter table t1 modify column `id` varchar(32); ERROR 1235 (0A000): Truncate th...
[=]value|MAX_ROWS [=]value|MIN_ROWS [=]value|PACK_KEYS [=] {0|1|DEFAULT}|PASSWORD [=]'string'|ROW_FORMAT [=] {DEFAULT|DYNAMIC|FIXED|COMPRESSED|REDUNDANT|COMPACT}|SECONDARY_ENGINE_ATTRIBUTE [=]'string'|STATS_AUTO_RECALC [=] {DEFAULT|0|1}|STATS_PERSISTENT [=] {DEFAULT|0|1}|STATS...