sql alter table alter column code example

Example 1: sql server alter column

ALTER TABLE table_name 
ALTER COLUMN column_name new_data_type(size);

Example 2: sql alter column size

ALTER TABLE table_name
ALTER COLUMN column_name datatype;

Example 3: sqlserver add column to table

ALTER TABLE dbo.doc_exa 
ADD column_b VARCHAR(20) NULL, 
	column_c INT NULL ;

Example 4: sql alter table

Adds, deletes or edits columns in a table. It can also be used to add and
delete constraints in a table, as per the above.
Example: Adds a new boolean column called ‘approved’ to a table named
‘deals’.
ALTER TABLE deals
ADD approved boolean;
Example 2: Deletes the ‘approved’ column from the ‘deals’ table
ALTER TABLE deals
DROP COLUMN approved;

Example 5: sql change column in existing table

'This adds 'NOT NULL' to excisting column counting in the table mytable'
ALTER TABLE mytable ALTER COLUMN counting INT NOT NULL;

Example 6: sql alter table

-- With check if field already exists

IF NOT EXISTS(SELECT 1 FROM sys.columns 
          WHERE Name = N'Email'
          AND Object_ID = Object_ID(N'dbo.Customers'))
BEGIN    
	ALTER TABLE Customers
    ADD Email varchar(255);
END