ALTER TABLE name add column name data class type
Example: ALTER TABLE Student add nickname char (20)
ALTER TABLE tableName (table name) add columnName (column name) varchar (30)
Modifying the type of a column
ALTER TABLE tbname--table name
Alter COLUMN COLNAME--column name
NvarChar (50)--Data type
Not NULL
ALTER TABLE s_part_no ALTER COLUMN rohs_grade varchar (NOT NULL)
ALTER TABLE s_part_no ALTER COLUMN Rohs_grade varchar (10)
Add columns
Alter table dbo. Wf_d_task_signer Add COMMENT NVARCHAR (400)
Delete Column
ALTER TABLE dbo. Wf_d_task_notification Drop Column task_id
ALTER TABLE dbo. Wf_d_task_notification Drop Column next_task_id
Determine if a column exists
SELECT * from syscolumns where id=object_id (' table name ') and name= ' column name '
SELECT * from syscolumns where id=object_id (' q_d_exception ') and name= ' Exception_type '
--Determine if the column exists and add if it does not exist
IF not EXISTS (SELECT 1 from sys.columns WHERE object_id = object_id (' q_d_exception ') and name = ' COMMENT ')
BEGIN
ALTER TABLE q_d_exception ADD COMMENT NVARCHAR ($) NULL;
END
Modify column names
Modify table name or field name with stored procedure sp_rename
exec sp_rename ' Q_d_inmr_header. [All_signed_date] ', ' signed_date ', ' column '
SQL Add column, delete column, modify column type