导出数据：
mysqldump -ppassword -u username dbname tableName > tableName.sql
mysqldump --user=user --password=pass db table --where="id=1" > dump.sql
导入数据：
mysql db_name < script.sql
查看外键约束：
SELECT
TABLE_NAME,
COLUMN_NAME,
CONSTRAINT_NAME,
REFERENCED_TABLE_NAME,
REFERENCED_COLUMN_NAME
FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE
WHERE REFERENCED_TABLE_NAME = 'My_Table';
全部的表：
SELECT TABLE_NAME, COLUMN_NAME, CONSTRAINT_NAME, REFERENCED_TABLE_NAME, REFERENCED_COLUMN_NAME FROM INFORMATION_SCHEMA.KEY_COLUMN_USAGE ;
去除约束：
ALTER TABLE table_name DROP FOREIGN KEY fk_constraint;
添加约束：
Alter Table Table1 Add Constraint [CONSTRAINTNAME] Foreign Key (Column) References Table2 (Column) On Update Cascade On Delete Cascade;
ALTER TABLE table_name ADD CONSTRAINT fk_constraint FOREIGN KEY (column) REFERENCES table2(column) On Update Cascade On Delete Cascade;
主键：
Alter Table Table add constraint [Primary Key] Primary key(Column1,Column2,.....)
约束不能更改，只能先移除再创建。
将id键复位到1：
ALTER TABLE table_name AUTO_INCREMENT = 1;
改变条目：
UPDATE table_name SET field1=new-value1, field2=new-value2 [WHERE Clause]
选择前10条：
select * from table1 limit 10
