SQL test query or validation query

 

Ref: https://stackoverflow.com/questions/3668506/efficient-sql-test-query-or-validation-query-that-will-work-across-all-or-most

Many database connection pooling libraries provide the ability to test their SQL connections for idleness. For example, the JDBC pooling library c3p0 has a property called preferredTestQuery, which gets executed on the connection at configured intervals. Similarly, Apache Commons DBCP has validationQuery.

-- Access

SELECT 1 FROM (SELECT count(*) dual FROM MSysResources) AS dual

-- BigQuery, CockroachDB, Exasol, H2, Ignite, MariaDB, MySQL, PostgreSQL, 

-- Redshift, Snowflake, SQLite, SQL Server, Sybase ASE, Vertica

SELECT 1

-- MemSQL, Oracle

SELECT 1 FROM DUAL

-- CUBRID

SELECT 1 FROM db_root

-- Db2

SELECT 1 FROM SYSIBM.DUAL

-- Derby

SELECT 1 FROM SYSIBM.SYSDUMMY1

-- Firebird

SELECT 1 FROM RDB$DATABASE

-- HANA, Sybase SQL Anywhere

SELECT 1 FROM SYS.DUMMY

-- HSQLDB

SELECT 1 FROM (VALUES(1)) AS dual(dual)

-- Informix

SELECT 1 FROM (SELECT 1 AS dual FROM systables WHERE (tabid = 1)) AS dual

-- Ingres, Teradata

SELECT 1 FROM (SELECT 1 AS "dual") AS "dual"