DELETE FROM + LEFT JOIN SNOWFLAKE

Question

我正在尝试使用 delete 从表中删除行。

delete a
from "table1" as a
LEFT JOIN "table2" AS b 
on a."x" = b."x" 
where b."X" = 'X'

但我得到的都是

SQL 编译错误：位置 7 的第 1 行语法错误意外“a”。位置 0 处出现语法错误第 3 行意外的“LEFT”。

你能帮帮我吗？

Answer 1

这是雪花中正确的语法：

delete from "table1" as a
USING "table2" as b 
WHERE a."x" = b."x" 
  and b."X" = 'X'

Answer 2

使用WHERE 并引用外部表中的特定值有效地使LEFT JOIN 成为INNER JOIN：

SELECT * -- DELETE a
FROM "table1" as a
LEFT JOIN "table2" AS b 
ON a."x" = b."x" 
WHERE b."X" = 'X';

---

行为相同：

SELECT *  -- DELETE a
FROM "table1" as a
INNER JOIN "table2" AS b 
ON a."x" = b."x" 
WHERE b."X" = 'X';

---

根据需求，它可以用EXISTS/NOT EXISTS重写：

DELETE FROM "table1"
WHERE NOT EXISTS (SELECT 1 
                 FROM "table2" 
                 WHERE "table1"."x" = "table2"."x"
                 AND "table2"."x" = 'X');