MySQL joins columns, changes columns, and deletes columns.

MySQL joins columns, changes columns, deletes columns

ALTER table: Add, change, delete table columns, constraints, and other table definitions.

• View column: Desc table name;
• Change table name: ALTER TABLE T_book Rename to BBB;
• Add column: ALTER TABLE name add column name varchar (30);
• Delete column: ALTER TABLE table name drop column name;
• Change Column name mysql:alter table BBB change nnnnn hh int;
• Change the column name sqlserver:exec sp_rename ' t_student.name ', ' nn ', ' column ';
• Change Column name oracle:lter table BBB Rename column nnnnn to HH int;
• Change column properties: ALTER TABLE T_book modify name varchar (22);

Sp_rename:sqlserver built-in stored procedures, with the definition of the change table.

MySQL view constraint, add constraint, delete constraint join column, change column, delete column

• View field information for table: DESC table name;
• View all information about the table: Show create table table name;
• Join? PRIMARY KEY constraint: ALTER TABLE name add constraint primary key (Shape: Pk_ table name) primary key table name (primary key field);
• Join? FOREIGN KEY constraint: ALTER TABLE from TABLE ADD constraint foreign key (shape: Fk_ from Table _ Main Table) foreign key from table (foreign key field) references Main Table (primary key field);
• Delete PRIMARY KEY constraint: ALTER TABLE name drop PRIMARY key;
• Delete FOREIGN KEY constraint: ALTER TABLE name drop FOREIGN key foreign key (distinguish uppercase and lowercase);

• change table name: ALTER TABLE T_book Rename to BBB;
• add column: ALTER TABLE name add column name varchar (+);
• delete column: ALTER TABLE table name drop column name;
• change column name Mysql:alter table bbb changes nnnnn hh int;
• change column name sqlserver:exec sp_rename ' T_student.name ', ' NN ', ' column ';
• change column name oracle:alter table BBB Rename column nnnnn to HH int;
• Change column properties: ALTER TABLE T_book modify name varchar;

Sp_rename:sqlserver built-in stored procedures, with the definition of the change table.