left outer join preserving unmatched rows from the first table

https://docs.oracle.com/javadb/10.8.3.0/ref/rrefsqlj18922.html

  • INNER JOIN operation

    Specifies a join between two tables with an explicit join clause.

  • LEFT OUTER JOIN operation

    Specifies a join between two tables with an explicit join clause, preserving unmatched rows from the first table.

  • RIGHT OUTER JOIN operation

    Specifies a join between two tables with an explicit join clause, preserving unmatched rows from the second table.

  • CROSS JOIN operation

    Specifies a join that produces the Cartesian product of two tables. It has no explicit join clause.

  • NATURAL JOIN operation

    Specifies an inner or outer join between two tables. It has no explicit join clause. Instead, one is created implicitly using the common columns from the two tables.

JOIN operations https://docs.oracle.com/javadb/10.8.3.0/ref/rrefsqlj29840.html

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原文地址：https://www.cnblogs.com/rsapaper/p/7784884.html