Changing new columns when altering a table

Use the Change Column window to modify new columns for the table that you're altering. You can change any field of any column you have added until you click on OK.

Fields and controls

To change a new column:

1. Make any of the following changes to the column definition:
   • Change the name of the column by typing a new name in the Column name field.
   • Use the Data type box to specify a different data type.
   • If the data type of the column is CHARACTER, VARCHAR, BLOB, CLOB, DBCLOB, GRAPHIC, or VARGRAPHIC, change the length of the column by typing a new length in the Length field.
   • If the data type of the column is BLOB, CLOB, or DBCLOB, use the LOB unit box to specify a new multiplier for the length of columns.
   • If the data type of the column is DECIMAL:
     1. In the Precision field, type the new precision (total number of digits) for the column.
     2. In the Scale field, type the new scale (number of digits to the right of the decimal) for the column.
   • If the data type of the column is BLOB, CLOB, DBCLOB, or a distinct type with any of these as source types, specify the LOB options by selecting or clearing the appropriate LOB option check boxes.
   • If the data type of the column is CHARACTER, VARCHAR, or LONG VARCHAR, select or clear the Bit data check box to specify whether the contents of the column be treated as bit (binary) data.
   • If you want to allow the column to contain null values, select the Nullable check box.
   • Optional: If you want the column to contain a default value, select the check box beside the Default field, and type the default value for the column.

     Note:

     You cannot specify a default value if you want the column to be a generated column.

   • Optional: In the Comment field, document the column that you're adding.
   • If you want DB2 to automatically generate values for the column, select Generate column contents.
     • If you want the column to be an identity column, select Identity.

       Note:

       An identity column must have a numeric data type.

       You can specify the following parameters:
       • Initial value to specify the value that will be generated for the first row of the table.
       • Increment to specify the incremental value for each row.
       • Cache value to specify how many identity row values DB2 will maintain in the cache.
       • By default to specify whether DB2 will generate a value for each row that you import or load into the table, even if the input data contains an identity value for the row.
     • If you want to specify the formula by which DB2 generates values, select Formula, and specify the formula.
   • Click on Apply to add the new column.

     You can add up to 500 columns to your table.

   • Click on Cancel to close the Add Column window.
2. Click on OK to make the changes you specified for the column and close the Change Column window.
3. If you do not want to make any additional changes to the table, click on OK to alter your table and close the Alter Table notebook. Otherwise, continue on to one or more of the optional tasks.

Related information

• Alter Table -- Overview
• Data types -- See the SQL Reference
• LOB units -- See the SQL Reference
• Default values -- See the SQL Reference
• Null values -- See the SQL Reference