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应用 (APPLY)

适用于 ✅ 开源版   ✅ 专业版   ✅ 企业版

APPLY(具体来说,CROSS APPLYOUTER APPLY)是 SQL Server 特有的 SQL 标准 LATERAL 派生表语法

一个例子

SELECT *
FROM
  AUTHOR

  -- All previous objects (i.e. AUTHOR)
  -- are now in scope for the following subquery
  CROSS APPLY (
    SELECT count(*)
    FROM BOOK
    WHERE BOOK.AUTHOR_ID = AUTHOR.ID -- AUTHOR is in scope
  );
DSL.using(configuration)
   .select()
   .from(
      AUTHOR
      .crossApply(
        select(count()
        .from(BOOK)
        .where(BOOK.AUTHOR_ID.eq(AUTHOR.ID)))
      )
   )
   .fetch();

这对于以下情况最有用:

方言支持

此示例使用 jOOQ

selectFrom(AUTHOR.crossApply(selectCount().from(BOOK).where(BOOK.AUTHOR_ID.eq(AUTHOR.ID))))

翻译成以下特定方言的表达式

Aurora Postgres, CockroachDB, DB2, Databricks, Firebird, Hana, Postgres, Snowflake, Trino, YugabyteDB

SELECT
  AUTHOR.ID,
  AUTHOR.FIRST_NAME,
  AUTHOR.LAST_NAME,
  AUTHOR.DATE_OF_BIRTH,
  AUTHOR.YEAR_OF_BIRTH,
  AUTHOR.DISTINGUISHED,
  alias_124651337.count
FROM AUTHOR
  CROSS JOIN LATERAL (
    SELECT count(*)
    FROM BOOK
    WHERE BOOK.AUTHOR_ID = AUTHOR.ID
  ) alias_124651337

Oracle, SQLDataWarehouse, SQLServer, Sybase

SELECT
  AUTHOR.ID,
  AUTHOR.FIRST_NAME,
  AUTHOR.LAST_NAME,
  AUTHOR.DATE_OF_BIRTH,
  AUTHOR.YEAR_OF_BIRTH,
  AUTHOR.DISTINGUISHED,
  alias_124651337.count
FROM AUTHOR
  CROSS APPLY (
    SELECT count(*)
    FROM BOOK
    WHERE BOOK.AUTHOR_ID = AUTHOR.ID
  ) alias_124651337

ASE, Access, Aurora MySQL, BigQuery, ClickHouse, Derby, DuckDB, Exasol, H2, HSQLDB, Informix, MariaDB, MemSQL, MySQL, Redshift, SQLite, Teradata, Vertica

/* 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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