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DECODE

Applies to ✅ Open Source Edition   ✅ Express Edition   ✅ Professional Edition   ✅ Enterprise Edition

Some SQL dialects, including Db2, H2, Oracle know a more succinct, but maybe less readable DECODE() function with a variable number of arguments. This function works like a NULL safe CASE expression. jOOQ supports the DECODE() function and emulates it using CASE expressions in all dialects that do not have native support:

SELECT
  -- Oracle:
  DECODE(FIRST_NAME, 'Paulo', 'brazilian',
                     'George', 'english',
                     'unknown'),
  -- Other SQL dialects
  CASE
    WHEN FIRST_NAME IS NOT DISTINCT FROM 'Paulo'  THEN 'brazilian'
    WHEN FIRST_NAME IS NOT DISTINCT FROM 'George' THEN 'english'
    ELSE 'unknown'
  END
FROM AUTHOR




// Use the Oracle-style DECODE() function with jOOQ.
// Note, that you will not be able to rely on type-safety
decode(
  AUTHOR.FIRST_NAME,
  "Paulo", "brazilian",
  "George", "english",
  "unknown"
);

See the DISTINCT predicate for details about the NULL safe semantics.

Dialect support

This example using jOOQ:

decode(AUTHOR.FIRST_NAME, "Paulo", "BR", "George", "EN", "unknown")

Translates to the following dialect specific expressions:

ASE, SQLDataWarehouse

CASE
  WHEN EXISTS (
    SELECT AUTHOR.FIRST_NAME x
    INTERSECT
    SELECT 'Paulo' x
  ) THEN 'BR'
  WHEN EXISTS (
    SELECT AUTHOR.FIRST_NAME x
    INTERSECT
    SELECT 'George' x
  ) THEN 'EN'
  ELSE 'unknown'
END

Aurora MySQL, MySQL

CASE
  WHEN (AUTHOR.FIRST_NAME <=> 'Paulo') THEN 'BR'
  WHEN (AUTHOR.FIRST_NAME <=> 'George') THEN 'EN'
  ELSE 'unknown'
END

Aurora Postgres, BigQuery, CockroachDB, DuckDB, Firebird, HSQLDB, Postgres, SQLServer, Snowflake, Trino, YugabyteDB

CASE
  WHEN AUTHOR.FIRST_NAME IS NOT DISTINCT FROM 'Paulo' THEN 'BR'
  WHEN AUTHOR.FIRST_NAME IS NOT DISTINCT FROM 'George' THEN 'EN'
  ELSE 'unknown'
END

ClickHouse

CASE
  WHEN arrayUniq(ARRAY(AUTHOR.FIRST_NAME, 'Paulo')) = 1 THEN 'BR'
  WHEN arrayUniq(ARRAY(AUTHOR.FIRST_NAME, 'George')) = 1 THEN 'EN'
  ELSE 'unknown'
END

DB2, Exasol, H2, Informix, MemSQL, Oracle, Teradata, Vertica

decode(
  AUTHOR.FIRST_NAME,
  'Paulo',
  'BR',
  'George',
  'EN',
  'unknown'
)

Derby

CASE
  WHEN EXISTS (
    SELECT AUTHOR.FIRST_NAME x
    FROM SYSIBM.SYSDUMMY1
    INTERSECT
    SELECT 'Paulo' x
    FROM SYSIBM.SYSDUMMY1
  ) THEN 'BR'
  WHEN EXISTS (
    SELECT AUTHOR.FIRST_NAME x
    FROM SYSIBM.SYSDUMMY1
    INTERSECT
    SELECT 'George' x
    FROM SYSIBM.SYSDUMMY1
  ) THEN 'EN'
  ELSE 'unknown'
END

Hana

map(
  AUTHOR.FIRST_NAME,
  'Paulo',
  'BR',
  'George',
  'EN',
  'unknown'
)

MariaDB

decode_oracle(
  AUTHOR.FIRST_NAME,
  'Paulo',
  'BR',
  'George',
  'EN',
  'unknown'
)

Redshift

CASE
  WHEN NOT (AUTHOR.FIRST_NAME IS DISTINCT FROM 'Paulo') THEN 'BR'
  WHEN NOT (AUTHOR.FIRST_NAME IS DISTINCT FROM 'George') THEN 'EN'
  ELSE 'unknown'
END

SQLite

CASE
  WHEN (AUTHOR.FIRST_NAME IS 'Paulo') THEN 'BR'
  WHEN (AUTHOR.FIRST_NAME IS 'George') THEN 'EN'
  ELSE 'unknown'
END

Sybase

CASE
  WHEN EXISTS (
    SELECT AUTHOR.FIRST_NAME x
    FROM SYS.DUMMY
    INTERSECT
    SELECT 'Paulo' x
    FROM SYS.DUMMY
  ) THEN 'BR'
  WHEN EXISTS (
    SELECT AUTHOR.FIRST_NAME x
    FROM SYS.DUMMY
    INTERSECT
    SELECT 'George' x
    FROM SYS.DUMMY
  ) THEN 'EN'
  ELSE 'unknown'
END

Access

/* UNSUPPORTED */
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