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適用于： Databricks SQL Databricks Runtime

根據聯結準則結合兩 個數據表參考 的資料列。

語法

left_table_reference { [ join_type ] JOIN right_table_reference join_criteria |
           NATURAL join_type JOIN right_table_reference |
           CROSS JOIN right_table_reference }

join_type
  { [ INNER ] |
    LEFT [ OUTER ] |
    [ LEFT ] SEMI |
    RIGHT [ OUTER ] |
    FULL [ OUTER ] |
    [ LEFT ] ANTI |
    CROSS }

join_criteria
  { ON boolean_expression |
    USING ( column_name [, ...] ) }

參數

• left_table_reference

  聯結左側的資料表參考。

• right_table_reference

  聯結右側的資料表參考。

• join_type

  聯結類型。

  • [ INNER ]

    傳回兩個數據表參考中具有相符值的資料列。 預設聯結類型。

  • LEFT [ OUTER ]

    傳回左資料表參考的所有值，以及右邊資料表參考的相符值，如果沒有相符值，則傳回 。 NULL 它也稱為 左外部聯結。

  • RIGHT [ OUTER ]

    傳回右資料表參考的所有值，以及來自左表參考的相符值，如果沒有相符值，則會附加 NULL 。 它也稱為 右外部聯結。

  • FULL [OUTER]

    傳回這兩個關聯的所有值，並將值附加 NULL 在不相符的端。 它也稱為 完整外部聯結。

  • [ LEFT ]半

    傳回資料表參考左邊的值，其與右邊相符。 也稱為 左半聯結。

  • [ LEFT ]反

    從左資料表參考傳回與右資料表參考不相符的值。 它也稱為 左反聯結。

• CROSS JOIN

  傳回兩個關聯性之笛卡兒乘積。

• 自然

  指定兩個關聯中的資料列會隱含地比對具有相符名稱的所有資料行是否相等。

• join_criteria

  指定一個資料表參考中的資料列如何與另一個資料表參考的資料列結合。

  • ON boolean_expression

    具有 BOOLEAN 之傳回類型的運算式，指定兩個關聯資料列的比對方式。 如果結果為 true，則會將資料列視為相符專案。

  • USING ( column_name [， ...] )

    比較兩個關聯中必須存在之資料行清單的 column_name 相等，以比對資料列。

    USING (c1, c2) 是 的 ON rel1.c1 = rel2.c1 AND rel1.c2 = rel2.c2 同義字。

• table_alias

  具有選擇性資料行識別碼清單的暫存名稱。

注意

當您指定 USING 或 NATURAL 時， SELECT * 每個用來比對的資料行只會顯示一個出現專案。

如果您省略 join_criteria 任何 join_type 的語意，就會變成 的 CROSS JOIN 語意。

例子

-- Use employee and department tables to demonstrate different type of joins.
> CREATE TEMP VIEW employee(id, name, deptno) AS
     VALUES(105, 'Chloe', 5),
           (103, 'Paul' , 3),
           (101, 'John' , 1),
           (102, 'Lisa' , 2),
           (104, 'Evan' , 4),
           (106, 'Amy'  , 6);

> CREATE TEMP VIEW department(deptno, deptname) AS
    VALUES(3, 'Engineering'),
          (2, 'Sales'      ),
          (1, 'Marketing'  );

-- Use employee and department tables to demonstrate inner join.
> SELECT id, name, employee.deptno, deptname
   FROM employee
   INNER JOIN department ON employee.deptno = department.deptno;
 103  Paul      3 Engineering
 101  John      1   Marketing
 102  Lisa      2       Sales

-- Use employee and department tables to demonstrate left join.
> SELECT id, name, employee.deptno, deptname
   FROM employee
   LEFT JOIN department ON employee.deptno = department.deptno;
 105 Chloe      5        NULL
 103  Paul      3 Engineering
 101  John      1   Marketing
 102  Lisa      2       Sales
 104  Evan      4        NULL
 106   Amy      6        NULL

-- Use employee and department tables to demonstrate right join.
> SELECT id, name, employee.deptno, deptname
    FROM employee
    RIGHT JOIN department ON employee.deptno = department.deptno;
 103  Paul      3 Engineering
 101  John      1   Marketing
 102  Lisa      2       Sales

-- Use employee and department tables to demonstrate full join.
> SELECT id, name, employee.deptno, deptname
    FROM employee
    FULL JOIN department ON employee.deptno = department.deptno;
 101  John      1   Marketing
 106   Amy      6        NULL
 103  Paul      3 Engineering
 105 Chloe      5        NULL
 104  Evan      4        NULL
 102  Lisa      2       Sales

-- Use employee and department tables to demonstrate cross join.
> SELECT id, name, employee.deptno, deptname
    FROM employee
    CROSS JOIN department;
 105 Chloe      5 Engineering
 105 Chloe      5   Marketing
 105 Chloe      5       Sales
 103  Paul      3 Engineering
 103  Paul      3   Marketing
 103  Paul      3       Sales
 101  John      1 Engineering
 101  John      1   Marketing
 101  John      1       Sales
 102  Lisa      2 Engineering
 102  Lisa      2   Marketing
 102  Lisa      2       Sales
 104  Evan      4 Engineering
 104  Evan      4   Marketing
 104  Evan      4       Sales
 106   Amy      4 Engineering
 106   Amy      4   Marketing
 106   Amy      4       Sales

-- Use employee and department tables to demonstrate semi join.
> SELECT *
    FROM employee
    SEMI JOIN department ON employee.deptno = department.deptno;
 103  Paul      3
 101  John      1
 102  Lisa      2

-- Use employee and department tables to demonstrate anti join.
> SELECT *
    FROM employee
    ANTI JOIN department ON employee.deptno = department.deptno;
 105 Chloe      5
 104  Evan      4
 106   Amy      6

-- Use employee and department tables to demonstrate lateral inner join.
> SELECT id, name, deptno, deptname
    FROM employee
    JOIN LATERAL (SELECT deptname
                    FROM department
                    WHERE employee.deptno = department.deptno);
 103 Paul    3  Engineering
 101 John    1  Marketing
 102 Lisa    2  Sales

-- Use employee and department tables to demonstrate lateral left join.
> SELECT id, name, deptno, deptname
    FROM employee
    LEFT JOIN LATERAL (SELECT deptname
                         FROM department
                         WHERE employee.deptno = department.deptno);
 105 Chloe   5      NULL
 103 Paul    3      Engineering
 101 John    1      Marketing
 102 Lisa    2      Sales
 104 Evan    4      NULL
 106 Amy     6      NULL

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