MATCHES and LIKE operators
Use the standard LIKE operator instead of the MATCHES
operator.
The MATCHES operator is specific to IBM®
Informix® SQL, at allows to compare a character string
column to a search pattern:
SELECT * FROM customer WHERE customer_name MATCHES "A*"The Genero language supports a MATCHES operator. Do not confuse the language MATCHES
operator (used in BDL instructions such as IF custname MATCHES "S*"), with the SQL
MATCHES operator (used in SQL statements). There is no problem in using the
MATCHES operator of BDL.
LIKE:SELECT * FROM customer WHERE customer_name LIKE "A%"MATCHES expressions using a string
constant are replaced by a LIKE expression.Only
MATCHES expressions with a string constant can be converted to
LIKE expressions, if the MATCHES uses a ? SQL
parameter place holder, no translation is done.
| Database Server Type | SQL MATCHES support |
|---|---|
| IBM DB2® LUW | Emulated, see details |
| IBM Informix | Yes, native SQL feature |
| IBM Netezza | Emulated, see details |
| Microsoft™ SQL Server | Emulated, see details |
| Oracle® MySQL / MariadDB | Emulated, see details |
| Oracle Database Server | Emulated, see details |
| PostgreSQL | Emulated, see details |
| SAP HANA® | Emulated, see details |
| SQLite | Emulated, see details |
For maximum portability, replace SQL MATCHES expressions by LIKE
expression. MATCHES uses * and ? as wildcards.
The equivalent wildcards in the LIKE operator are % and
_.
MATCHES character ranges such as [a-z]
cannot be converted for the LIKE operator.
Pay attention to blank padding semantics of the target database when using a program variable in
static SQL or a ? SQL parameter place holder after the LIKE
operator: If the program variable is defined as a CHAR(N), it is filled by the
runtime system with trailing blanks, in order to have a size of N, and the actual pattern for the
LIKE operator will contain trailing blanks. For example, when a CHAR(10) variable
is assigned with "ABC%", it will in fact contain "ABC% "
(with 6 additional blanks). When used as SQL parameter for a LIKE expression, the
database server will search for column values matching "ABC"+ some characters + 6 blanks. To avoid
this, use a VARCHAR(N) data type instead of CHAR(N) to hold
LIKE patterns.
Some database engines have specific semantics for the LIKE operator, especially
when using CHAR(N) data types. For example, with Oracle DB, the expression custname LIKE '%h': If
custname is defined as CHAR(30), Oracle will only find the rows when the custname values end
with a 'h' at the last character position (30). Values such as
'Smith' will not match. Similarly, when doing custname LIKE 'ab_',
rows where the column type is CHAR(N>3), values such as 'abc' will
not match in Oracle, IBM DB2 and PostgreSQL, because of the
significant trailing blanks.
As a general advice, use the VARCHAR type for variable string data, and leave
CHAR usage for fixed-length character string data such as codes.
PostgreSQL provides the SIMILAR TO operator, allowing
[start-end] character range specification as
in MATCHES.