1. alter-foreign-keys-method=drop_swap关闭外键检查直接 rename 新表 to 老表 2. alter-foreign-keys-method=rebuild_constraints完整重键所有子表约束 第一种操作的流程是 1. Disable foreign key checks for the session (FOREIGN_KEY_CHECKS=0) 2. Drop the table T1_old 3. Rename the new table _T1...
FOREIGN KEY 外键约束 CHECK 检查约束 DEFAULT 默认值约束 注意: MySQL不支持check约束,但可以使用check约束,而没有任何效果 如何添加/ 删除约束? CREATE TABLE时添加约束 ALTER TABLE时增加约束、删除约束 查看某个表已有的约束 #information_schema数据库名(系统库) #table_constraints表名称(专门存储各个表的约束...
SELECT * FROM information_schema.table_constraints WHERE table_name = '表名称';#查看某个表的约束名 ALTER TABLE 从表名 DROP FOREIGN KEY 外键约束名; (2)第二步查看索引名和删除索引。(注意,只能手动删除) SHOW INDEX FROM 表名称; #查看某个表的索引名ALTER TABLE 从表名 DROP INDEX 索引名; 6.4开...
PRIMARY KEY 主键约束,非空且唯一 FOREIGN KEY 外键约束 CHECH 检查约束 MYSQL中不支持CHECK约束,但可以使用而无任何作用 DEFAULT 默认值约束 4.如何查看表中的约束? SELECT * FROM infomation_schema.table_constraints WHERE table_name = `表名称` 1. 2. 3. 二.对约束的具体介绍 1.非空约束(NOT NULL) 作...
MySQL supports foreign keys, which permit cross-referencing related data across tables, and foreign key constraints, which help keep the related data consistent. A foreign key relationship involves a parent table that holds the initial column values, and a child table with column values that refer...
Let's load the table with different data: -- Now states table has different dataINSERTINTOstatesVALUES('CA','California'); You can see that this approach allows you to drop the parent table, leave foreign key constraints for the child tables, but it does not validate the new data loaded...
the row with country_id = 1 is being deleted since FK constraints are being ignored.How to repeat:CREATE DATABASE pt_osc; -- Query OK, 1 row affected (0.01 sec) USE pt_osc; -- Database changed SET foreign_key_checks=0; -- Query OK, 0 rows affected (0.01 sec) CREATE TABLE `cou...
MySQL requires that foreign key columns be indexed; if you create a table with a foreign key constraint but no index on a given column, an index is created. You can obtain information about foreign keys from the Information SchemaKEY_COLUMN_USAGEtable. An example of a query against this tab...
FOREIGN KEY外键约束 CHECK检查约束 DEFAULT默认值约束 查看某个表已有的约束 #information_schema数据库名(系统库)#table_constraints表名称(专门存储各个表的约束)SELECT * FROM information_schema.table_constraintsWHERE table_name = '表名称'; 2.非空约束 ...
MySQLMySQL Table Video Player is loading. Current Time0:00 / Duration-:- Loaded:0% Create a Table With Constraints in MySQL Drop Constraint From the MySQL Table The constraint is a set of rules or restrictions prohibiting the data entry in the MySQL columns. The table in MySQL has various...