In this tutorial, you have learned how to use the SQL Server ALTER TABLE ALTER COLUMN to modify some properties of an existing column. If you want to add the NOT NULL constraint to the column c, you must update NULL to non-null first for example: UPDATE t3Īnd then add the NOT NULL constraint: ALTER TABLE t3 ALTER COLUMN c VARCHAR ( 20) NOT NULL The following statement inserts some rows into the table: INSERT INTO t3 The following statement creates a new table with a nullable column: CREATE TABLE t3 (c VARCHAR( 50)) Code language: SQL (Structured Query Language) ( sql ) Add a NOT NULL constraint to a nullable column SQL Server issued the following error: String or binary data would be truncated. If the conversion fails, SQL Server terminates the statement and issues an error message.įor example, if you decrease the size of column c to 5 characters: ALTER TABLE t2 ALTER COLUMN c VARCHAR ( 5) Code language: SQL (Structured Query Language) ( sql ) However, when you decrease the size of the column, SQL Server checks the existing data to see if it can convert data based on the new size. You can increase the size of the column as follows: ALTER TABLE t2 ALTER COLUMN c VARCHAR ( 50) Let’s insert some sample data into the t2 table: INSERT INTO t2 If the function is an SQL table function, the function is reevaluated at alter time with the new column attributes. If there is a package associated with the function or procedure, it is invalidated. The following statement creates a new table with one column whose data type is VARCHAR(10): CREATE TABLE t2 (c VARCHAR( 10)) Alter of a column referenced in the body of a user-defined function or procedure. Code language: SQL (Structured Query Language) ( sql ) Change the size of a column SQL Server issued the following error: Conversion failed when converting the varchar value to data type int. VALUES ( language: SQL (Structured Query Language) ( sql )įourth, modify the data type of the column from VARCHAR back to INT: ALTER TABLE t1 ALTER COLUMN c INT Third, insert a new row with a character string data: INSERT INTO t1 Second, modify the data type of the column from INT to VARCHAR: ALTER TABLE t1 ALTER COLUMN c VARCHAR ( 2) Second, insert some rows into the table: INSERT INTO t1 The new data type must be compatible with the old one, otherwise, you will get a conversion error in case the column has data and it fails to convert.įirst, create a new table with one column whose data type is INT: CREATE TABLE t1 (c INT) To modify the data type of a column, you use the following statement: ALTER TABLE table_nameĪLTER COLUMN column_name new_data_type( size) Ĭode language: SQL (Structured Query Language) ( sql ) SQL Server allows you to perform the following changes to an existing column of a table: Summary: in this tutorial, you will learn how to use the SQL Server ALTER TABLE ALTER COLUMN statement to modify a column of a table. method_nameĪpplies to: SQL Server 2008 (10.0.x) and later, SQL Database. For information, see the Best Practices, General Remarks, and Limitations and Restrictions sections that follow. You can use the optional BEGIN and END keywords to enclose the statements. To change a sequence's schema, you must also have CREATE privilege on the new schema. You must own the sequence to use ALTER SEQUENCE. Any parameters not specifically set in the ALTER SEQUENCE command retain their prior settings. One or more Transact-SQL statements comprising the body of the procedure. ALTER SEQUENCE changes the parameters of an existing sequence generator. Transact-SQL syntax for stored procedures in SQL Server and Azure SQL Database: CREATE Jump to Simple Examples to skip the details of the syntax and get to a quick example of a basic stored procedure. ![]() ![]() CLR integration does not apply to Azure SQL Database. NET Framework CLR into SQL Server is discussed in this topic.
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