ALTER TABLE语句的基本语法如下: ALTERTABLEtable_nameDROPCOLUMNcolumn_name1,DROPCOLUMNcolumn_name2,... 1. 2. 3. 4. 在上面的语法中,table_name是你要修改的表的名称,column_name1、column_name2等是要删除的列的名称。你可以根据需要删除多个列,只需在DROP COLUMN关键字之后列出要删除的每个列名即可。 示...
这里的database_name应该替换为你的数据库的名称。 步骤3:使用 ALTER TABLE 命令添加列 ALTERTABLEtable_nameADDCOLUMNcolumn1 datatype,ADDCOLUMNcolumn2 datatype; 1. 2. 3. 在这里,table_name是需要修改的表的名称,column1和column2是要添加的列的名称,datatype是列的数据类型。 饼状图示例 17%33%50%添加...
If you wish to create a composite primary key you can select multiple columns and check the PK check box. However, there is an additional step that is required, you must click the Indexes tab, then in the Index Columns panel you must set the desired order of the primary keys. ...
ALTER TABLE foo MODIFY COLUMN a ..., MODIFY COLUMN b ..., etc; It is usually more efficient to collect all your alters into one statement. Subject Written By Posted how to alter multiple columns siva shanmugam November 07, 2008 12:36AM ...
Generated columns can be added. CREATETABLEt1(c1INT);ALTERTABLEt1ADDCOLUMNc2INTGENERATEDALWAYSAS(c1+1)STORED; The data type and expression of generated columns can be modified. CREATETABLEt1(c1INT,c2INTGENERATEDALWAYSAS(c1+1)STORED);ALTERTABLEt1MODIFYCOLUMNc2TINYINTGENERATEDALWAYSAS(c1+5)STORED;...
You have a "huge" table, and you need to ALTER it. By "huge" I mean that the ALTER would take an unacceptable amount of time. Things you might want to do. and for which this is well suited: ⚈ Add/drop columns ⚈ Modify datatypes (INT -> BIGINT, SIGNED -> UNSIGNED) ...
Summary: in this tutorial, you will learn about the MySQL ALTER TABLE statement that changes existing table structure such as adding or removing columns, changing column attributes, etc.Introduction to MySQL ALTER TABLE statement#You use the ALTER TABLE statement to change the structure of existing...
Changing columns using MySQL ALTER TABLE statement Using MySQL ALTER TABLE statement to set auto-increment attribute for a column Suppose you want the value of the task_id column to be increased automatically by one whenever you insert a new record into the tasks table. To do this, you use ...
Copyselect 'alter table '||a.TABLE_NAME||' modify '||a.COLUMN_NAME||' VARCHAR2('||data_length||');' from all_tab_columns a where a.data_type='CHAR' AND OWNER='用户名'; 通过rtrim 函数把数据右边的空格清除掉 Copyupdate 表名set 列名1=rtrim(列名1); ...
alter table tbl add column rowid int(11) NOT NULL AUTO_INCREMENT primary key; alter table tbl ENGINE=InnoDB DEFAULT CHARSET=latin1 COLLATE=latin1_bin; And to know which tables that needs to be altered, I do the following: SELECT DISTINCT TABLE_NAME FROM INFORMATION_SCHEMA.COLUMNS WHE...