mysql alter column not null

> ALTER TABLE myTable -> ADD COLUMN Quantity SMALLINT UNSIGNED NOT NULL, -> MODIFY ID SMALLINT UNSIGNED NOT NULL, -> ADD PRIMARY KEY (ID); Run the desc command again to view the table structure. The preceding modification command takes effect: Desc myTable;+ ---------- + ---------------------- + ------ + ----- +

The following articles mainly introduce the practical use of MySQL ALTER syntax. We all know that the proportion of MySQL ALTER syntax in actual application is still very large, so you can have a good idea about the practical use of MySQL

// Primary key Alter table tablename add new_field_id int (5) unsigned default 0 not null anto_increment, add primary key (new_field_id ); // Add a new columnMysql> alter table tablename ADD fieldname fieldtypeFor example:Alter table t2 ADD d TIMESTAMP;Alter table infos ADD ex tinyint not

statement: mysql> ALTER TABLE myTable -> ADD COLUMN Quantity SMALLINT UNSIGNED not NULL, -> MODIFY ID SMALL INT UNSIGNED not NULL, -> ADD PRIMARY KEY (ID); Again using the DESC command to view the table structure, we found that the above modification

// Primary keyAlter table tablename add new_field_id int (5) unsigned default 0 not null anto_increment, add primary key (new_field_id );// Add a new columnMysql> alter table tablename ADD fieldname fieldtypeFor example:Alter table t2 ADD d TIMESTAMP;Alter table infos ADD ex tinyint not null default '0 ';// Delete a co

I field of the table created above: mysql> ALTER TABLE testalter_tbl DROP i; You cannot use drop to delete a field if only one field is left in the datasheet. In MySQL, use the ADD clause to add columns to the datasheet, the following instance adds the I field in the table Testalter_tbl, and defines the data type:

Mysql adds a column, deletes a column, modifies a column name, and mysql columns at a certain position in the table. To add a column to a created table, run the following code: alter t

test where ID mysql> TRUNCATE TABLE test; #删除allMysql> select * from test;Empty Set (0.00 sec) On top, modify the table name in the database, add and remove fields from the table. mysql> Use GBK #进入gbk数据库mysql> desc test;+-------+----------+------+-----+---------+----------------+| Field | Type | Null | Key | Defaul

Tags: color add char log alt usage RIP name testOne: Modify table information 1. Modify the table name Alter Table to Sys_app; 2. Modify Table Annotations Alter Table ' System Information Table '; Second: Modify field information 1. modifying field types and annotations Alter table sys_application columnvarchar( name of ' app ') ; 2. Modify the field type

We know that,MySQLDatabases are often combined with PHP to develop powerful applications. So for those who are new to PHP programming, it is necessary to understand some simple MySQL database operations. In this article, we useAlter tableStatement to modify the table structure. Next let's take a look at this part. 1. Add Columns Alter table tbl_name add col_name type For example, add a weight

original varchar (25) to varchar (20) Modify Field name The Code is as follows: Mysql> alter table person change stu_name name varchar (25 ); Query OK, 0 rows affected (0.20 sec) Records: 0 Duplicates: 0 Warnings: 0 Stu_name is the original name and name is the new name. It should be noted that no matter whether the data type is changed, the subsequent data types must be written If you do not modify th