Outer joins

Use standard ISO outer join syntax instead of the old IBM® Informix® OUTER() syntax.

Old IBM Informix SQL outer joins specified with the OUTER keyword in the FROM part are not standard:
SELECT * FROM master, OUTER ( detail )
  WHERE master.mid = detail.mid
    AND master.cdate IS NOT NULL
Table 1. Informix OUTER JOIN syntax by database brand
Database Server Type Informix OUTER join support
IBM Informix Yes, native SQL feature
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
Dameng® Emulated, see details
Most recent database servers now support the standard ANSI outer join specification:
SELECT * FROM master LEFT OUTER JOIN detail ON (master.mid = detail.mid)
  WHERE master.cdate IS NOT NULL

it is recommended that you use recent database servers and use ANSI outer joins only.