| SQL adaptation guide for IBM DB2 UDB 10.x / Data manipulation | |
Informix® supports MATCHES and LIKE in SQL statements, while IBM® DB2® supports the LIKE statement only.
MATCHES requires * and ? wild-card characters, and LIKE uses the % and _ wild-cards was equivalents.
( col MATCHES 'Smi*' AND col NOT MATCHES 'R?x' ) ( col LIKE 'Smi%' AND col NOT LIKE 'R_x' )
MATCHES allows you to use brackets to specify a set of matching characters at a given position:
( col MATCHES '[Pp]aris' ) ( col MATCHES '[0-9][a-z]*' )
The IBM DB2 LIKE operator has no operator for [ ] brackets character ranges.
With IBM DB2 , columns defined as CHAR(N) are blank padded, and trailing blanks are significant in the LIKE expressions. As result, with a CHAR(5) value such as 'abc ' (with 2 trailing blanks), the expression (colname LIKE 'ab_') will not match. To workaround this behavior, you can do (RTRIM(colname) LIKE 'pattern'). However, consider adding the condition AND (colname LIKE 'patten%') to force the DB server to optimize the query of the column is indexed. The CONSTRUCT instruction uses this technique when the entered criteria does not end with a * star wildcard.
The database driver is able to translate Informix MATCHES expressions to LIKE expressions, when no [ ] bracket character ranges are used in the MATCHES operand.
However, for maximum portability, consider replacing the MATCHES expressions to LIKE expressions in all SQL statements of your programs.
Avoid using CHAR(N) types for variable length character data (such as name, address).
See also: MATCHES and LIKE operators.