clickhouse : 使用 IN 左连接

Question

我希望基于两个条件执行左连接：

SELECT
  ...
FROM
   sometable AS a
LEFT JOIN someothertable AS b ON a.some_id = b.some_id 
  AND b.other_id IN (1, 2, 3, 4)

我得到了错误：

支持的语法：JOIN ON Expr([table.]column, ...) = Expr([table.]column, ...) [AND Expr([table.]column, ...) = Expr( [table.]column, ...) ...]```

看来join的条件必须是=，不能是in

有什么想法吗？

Answer 1

考虑将 IN 运算符移动到子查询中：

SELECT
    a.number,
    b.number
FROM numbers(8) AS a
LEFT JOIN 
(
    SELECT *
    FROM numbers(234)
    WHERE number IN (1, 2, 3, 4)
) AS b USING (number)

/*
┌─number─┬─b.number─┐
│      0 │        0 │
│      1 │        1 │
│      2 │        2 │
│      3 │        3 │
│      4 │        4 │
│      5 │        0 │
│      6 │        0 │
│      7 │        0 │
└────────┴──────────┘
*/

或

SELECT
    a.number,
    b.number
FROM numbers(8) AS a
LEFT JOIN 
(
    SELECT *
    FROM numbers(234)
    WHERE number IN (1, 2, 3, 4)
) AS b USING (number)
SETTINGS join_use_nulls = 1 /* 1 is 'JOIN behaves the same way as in standard SQL. The type of the corresponding field is converted to Nullable, and empty cells are filled with NULL.' */

/*
┌─number─┬─b.number─┐
│      0 │     ᴺᵁᴸᴸ │
│      1 │        1 │
│      2 │        2 │
│      3 │        3 │
│      4 │        4 │
│      5 │     ᴺᵁᴸᴸ │
│      6 │     ᴺᵁᴸᴸ │
│      7 │     ᴺᵁᴸᴸ │
└────────┴──────────┘
*/