null
BigQuery
Db2 (LUW)
MariaDB
MySQL
Oracle DB
PostgreSQL
SQL Server
SQLite
2005
2007
2009
2011
2013
2015
2017
2019
2021
✓ 3.5.7+
✓ 2012+
b
✓ 2008R2
✓ 9.1+
b
✓ 8.4 - 9.0
⚠ 8.3
⚠ 11gR1 - 21c
a
b
✓ 5.0+
✓ 5.1+
✓ 9.7+
✓ 2.0+
Empty string
is null
.
||
treats
null
as empty string
concat()
treats
null
as empty string