计算列
适用于 ❌ 开源版 ✅ Express 版 ✅ 专业版 ✅ 企业版
计算列，有时也称为“虚拟”列，是由同一行中其他列的表达式直接在数据库中生成的列。它们不能被写入，但可以在投影、过滤器，甚至 索引中使用，作为基于函数的索引的补充或替代。
像任何其他数据类型修改标志一样，生成器表达式可以在使用计算列创建表时传递给 jOOQ 中的数据类型
方言支持
此示例使用 jOOQ
createTable(name("x"))
.column(name("interest"), DOUBLE)
.column(name("interest_percent"), VARCHAR.generatedAlwaysAs(field(name("interest"), DOUBLE).times(100.0).concat(" %")))
翻译成以下特定方言的表达式
Aurora Postgres, Postgres
CREATE TABLE x ( interest double precision, interest_percent varchar GENERATED ALWAYS AS ((CAST((interest * CAST(1E2 AS double precision)) AS varchar) || ' %')) STORED )
ClickHouse
CREATE TABLE x ( interest Nullable(double), interest_percent Nullable(String) MATERIALIZED (CAST((interest * 1E2) AS Nullable(String)) || ' %') ) ENGINE Log()
CockroachDB
CREATE TABLE x ( interest double precision, interest_percent string GENERATED ALWAYS AS ((CAST((interest * CAST(1E2 AS double precision)) AS string) || ' %')) STORED )
Databricks
CREATE TABLE x ( interest double, interest_percent varchar(2147483647) GENERATED ALWAYS AS ((CAST((interest * 1E2) AS varchar(2147483647)) || ' %')) ) TBLPROPERTIES( 'delta.columnMapping.mode' = 'name', 'delta.feature.allowColumnDefaults' = 'supported' )
DB2
CREATE TABLE x ( interest double, interest_percent varchar(32672) GENERATED ALWAYS AS ((CAST((interest * CAST(1E2 AS double)) AS varchar(32672)) || ' %')) )
Derby
CREATE TABLE x ( interest double, interest_percent varchar(32672) GENERATED ALWAYS AS ((TRIM(CAST(CAST((interest * 1E2) AS char(38)) AS varchar(32672))) || ' %')) )
DuckDB, Hana
CREATE TABLE x ( interest double, interest_percent varchar GENERATED ALWAYS AS ((CAST((interest * 1E2) AS varchar) || ' %')) )
Firebird
CREATE TABLE x ( interest double precision, interest_percent varchar(4000) GENERATED ALWAYS AS ((CAST((interest * CAST(1E2 AS double precision)) AS varchar(4000)) || ' %')) )
H2
CREATE TABLE x ( interest double, interest_percent varchar AS ((CAST((interest * CAST(1E2 AS double)) AS varchar) || ' %')) )
HSQLDB
CREATE TABLE x ( interest double, interest_percent varchar(32672) GENERATED ALWAYS AS ((CAST((interest * 1E2) AS varchar(32672)) || ' %')) )
MariaDB, MySQL
CREATE TABLE x (
interest double,
interest_percent text GENERATED ALWAYS AS (concat(
CAST((interest * 1E2) AS char),
' %'
))
)
Oracle
CREATE TABLE x ( interest float, interest_percent varchar2(4000) GENERATED ALWAYS AS ((CAST((interest * 1E2) AS varchar2(4000)) || ' %')) )
SQLServer
CREATE TABLE x ( interest float, interest_percent AS (CAST((interest * CAST(1E2 AS float)) AS varchar(max)) + ' %') )
ASE, Access, Aurora MySQL, BigQuery, Exasol, Informix, MemSQL, Redshift, SQLDataWarehouse, SQLite, Snowflake, Sybase, Teradata, Trino, Vertica, YugabyteDB
/* UNSUPPORTED */
使用 jOOQ 3.21 生成。早期 jOOQ 版本的支持可能有所不同。 在我们的网站上翻译您自己的 SQL
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