BigQuery a Db2 (LUW) b d MariaDB c d MySQL c d Oracle DB e PostgreSQL SQL Server d SQLite d f g extract(… from ) extract(… from ) cast( as date) cast( as time) Despite its maturity and relevance, extract is still not supported by all major databases yet. SQL extract was available in SQL-92 ( intermediate) and is now part of the optional feature F052, “Intervals and datetime arithmetic”. The effect is basically like the following cast expression in standard SQL: CAST(CAST( AS DATE) AS TIMESTAMP) Compatibility Note that the result still has the time components-they are just set to zero. To use the date only-without time components-it is common practice to use the proprietary trunc function to set all time fields to zero ( 0): trunc() 2 A type conversion ( cast) to date therefore does not drop the time component in the Oracle database. Even the Oracle type date has a time component-in this regard, Oracle date is more like the standard timestamp. The Oracle database doesn’t have a predefined date type without time components. For more on this, see “ Inappropriate Use in The Where Clause” below. In the where clause, it is often the wrong choice. This is particularly useful for the group by clause. To extract the full date (year, month, day) or time (hour, minute, second) from a timestamp, cast can be used: 1 CAST( AS ) MeaningĮxtract can only get single fields. 0 The following table lists the extract fields defined by the SQL standard. SQL extract returns an exact numeric value. The field names are SQL keywords too-you must not put them in double or single quotes. SQL extract uses the keyword from to separate the field name from the value. SQL extract provides access to the components of temporal data types-i.e.
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