The ALTER TABLE instruction

Informix^® and IBM^® DB2^® use different implementations of the ALTER TABLE instruction. For example:

• Informix allows you to use multiple ADD clauses separated by commas. DB2 does not expect parentheses and the comma separator:

  Informix:

  ALTER TABLE customer ADD(col1 INTEGER), ADD(col2 CHAR(20))

  IBM DB2:

  ALTER TABLE customer ADD col1 INTEGER ADD col2 CHAR(20)

• Depending on the values currently stored, Informix can change the data type of a column, while DB2 only supports changing the size of CHAR and VARCHAR columns:

  Informix:

  ALTER TABLE customer MODIFY ( col1 INTEGER )

  IBM DB2:

  ALTER TABLE customer ALTER COLUMN col1 SET data type VARCHAR(200)