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CHANGE DATA TYPE

Function

This command is used to change the data type from INT to BIGINT or decimal precision from lower to higher.

Syntax

ALTER TABLE [db_name.]table_name CHANGE col_name col_name changed_column_type;

Parameter Description

Table 1 CHANGE DATA TYPE parameters

Parameter

Description

db_name

Name of the database. If this parameter is left unspecified, the current database is selected.

table_name

Name of the table.

col_name

Name of columns in a table. Column names contain letters, digits, and underscores (_).

changed_column_type

The change in the data type.

Usage Guidelines

  • Change of decimal data type from lower precision to higher precision will only be supported for cases where there is no data loss.

    Example:

    • Invalid scenario - Change of decimal precision from (10,2) to (10,5) is not valid as in this case only scale is increased but total number of digits remain the same.
    • Valid scenario - Change of decimal precision from (10,2) to (12,3) is valid as the total number of digits are increased by 2 but scale is increased only by 1 which will not lead to any data loss.
  • The allowed range is 38,38 (precision, scale) and is a valid upper case scenario which is not resulting in data loss.

Examples

  • Changing data type of column a1 from INT to BIGINT.

    ALTER TABLE test_db.carbon CHANGE a1 a1 BIGINT;

  • Changing decimal precision of column a1 from 10 to 18.

    ALTER TABLE test_db.carbon CHANGE a1 a1 DECIMAL(18,2);

System Response

By running DESCRIBE command, the changed data type for the modified column is displayed.

Parent topic: DDL