mysql - MySQL反向匹配

Question

我有以下脚本，它显示了 ADATA 表和 CDATA 表中记录的数据，由名字和姓氏匹配（我拥有的唯一字段在两个表中都是相同的）：

SELECT
c.asdf AS ASDF,
CONCAT(a.genr, ' ' ,a.firstname, ' ' ,a.lastname) AS Name,
a.rcvdate AS Report_Date,
c.enroll AS Enroll_Date,
a.cvb AS CVB,
c.pctcomp AS Percent_Complete

FROM
adata a,
cdatas c

WHERE
a.firstname = c.firstname
AND a.lastname = c.lastname

从这里我需要做的是获取 ADATA 中但不在 CDATA 中的记录列表，以及 CDATA 中不在 ADATA 中的记录。我尝试了在脚本的 WHERE 部分中使用的所有不同变体，NOT但总是给我 800 - ADATA 中的记录总数（CDATA 表只有 130 条记录）。

有没有办法正确地做到这一点？

Answer 1

SELECT columns
FROM
    adata a
    LEFT JOIN cdatas c ON (a.firstname = c.firstname AND a.lastname = c.lastname)
WHERE
    c.asdf IS NULL
UNION ALL
SELECT columns
FROM
    cdatas c
    LEFT JOIN adata a ON (c.firstname = a.firstname AND c.lastname = a.lastname)
WHERE
    a.cvb IS NULL

Answer 2

mysql> create table a (x int);
mysql> create table b (y int);
mysql> insert into a values (1), (2), (3), (4), (5);
mysql> insert into b values (2), (4), (6);
mysql> select x from a where not x in (select y from b);
+------+
| x    |
+------+
|    1 |
|    3 |
|    5 |
+------+
mysql> select y from b where not y in (select x from a);
+------+
| y    |
+------+
|    6 |
+------+