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SQL programming
You can use the HCL Informix® implementation of the SQL language to develop applications for Informix database servers.
Guide to SQL: Tutorial
The Informix® Guide to SQL: Tutorial shows how to use basic and advanced structured query language (SQL) to access and manipulate the data in your databases. It discusses the data manipulation language (DML) statements as well as triggers and stored procedure language (SPL) routines, which DML statements often use.
Create and use triggers
Re-entrant triggers

SQL programming
You can use the HCL Informix® implementation of the SQL language to develop applications for Informix database servers.
- Guide to SQL: Syntax
- Guide to SQL: Reference
  The Informix® Guide to SQL: Reference contains the reference information for the system catalog tables, data types, and environment variables of the HCL Informix dialect of the SQL language, as implemented in HCL Informix. These topics also include information about the stores_demo, sales_demo, and superstore_demo databases that are included with HCL Informix.
- Guide to SQL: Tutorial
  The Informix® Guide to SQL: Tutorial shows how to use basic and advanced structured query language (SQL) to access and manipulate the data in your databases. It discusses the data manipulation language (DML) statements as well as triggers and stored procedure language (SPL) routines, which DML statements often use.

Re-entrant triggers

A re-entrant trigger refers to a case in which the triggered action can reference the triggering table. In other words, both the triggering event and the triggered action can operate on the same table. For example, suppose the following UPDATE statement represents the triggering event:

UPDATE tab1 SET (col_a, col_b) = (col_a + 1, col_b + 1);

The following triggered action is legal because column col_c is not a column that the triggering event has updated:

UPDATE tab1 SET (col_c) = (col_c + 3);

In the preceding example, a triggered action on col_a or col_b would be illegal because a triggered action cannot be an UPDATE statement that references a column that was updated by the triggering event.

Important: Select triggers cannot be re-entrant triggers. If the triggering event is a SELECT statement, the triggered action cannot operate on the same table.

For a list of the rules that describe those situations in which a trigger can and cannot be re-entrant, see the CREATE TRIGGER statement in the Informix® Guide to SQL: Syntax.