将变量分配给 PL/SQL 块内的子查询结果

Question

这是一些更简化的伪代码，描述了我正在尝试做的事情：

DECLARE
  CURSOR CURSOR_A IS
    SELECT FIELD_A1, FIELD_A2
    FROM TABLE_A;
vNAME NVARCHAR2(100) := NULL;
BEGIN
FOR RECORD_A IN CURSOR_A LOOP
  IF (RECORD_A.FIELD_A1 IS NOT NULL) THEN
    vNAME := RECORD_A.FIELD_A1;
  ELSE
    vNAME := (SELECT FIELD_B
                FROM TABLE_B
               WHERE TABLE_B.B2 = RECORD_A.A2)
END LOOP;
END;
/

不允许在 PL/SQL 块中包含 SELECT 语句吗？

Answer 1

所有你需要的 - 一个选择。尝试一下：

declare
    name nvarchar2(100) := null;
begin
    for row_ in (
        select field_a1, field_b from table_a left outer join table_b on b2 = a2
    ) loop
        name := coalesce(row_.field_a1, row_.field_b);
        -- do something
    end loop;
end;
/

... and field_a1 is null如果您在两个表中都有太多行并且担心性能，您仍然可以添加到 on-clause。