使用 XOR 语句连接子句

Question

我正在执行连接，但我似乎无法使此 XOR 正常工作。

SELECT t1.COMPANY, t1.MILES,
   CASE WHEN t2.MILES IS NULL THEN t3.MILES
        ELSE t2.MILES
   END AS MILES2,
   CASE WHEN t2.MILES = t1.MILES AND t2.MILES != 9999 THEN t2.FLATRATE
        ELSE t3.RATEBASIS
   END AS RATE           
FROM TABLE1 AS t1
    LEFT JOIN TABLE2 AS t2 
        ON t1.[COMPANY] = t2.[COMPANYCODE] AND (t1.[MILES] = t2.[MILES])
    INNER JOIN (
         SELECT TOP 1 TRUCKERCODE, MILES, RATEBASIS, FLATRATE FROM TABLE2 WHERE MILES = 9999
               ) AS t3 
   ON t1.[COMPANY] = t3.[COMPANYCODE]

如果英里数相同，我需要加入 ON 子句，然后获取匹配的给定字段，否则我需要从第二个表中获取的默认数据是英里数等于 9999 的位置。现在使用那个 ON子句我得到许多额外的行，其中 MILES 等于 45，它从 TABLE2 获取数据，其中英里等于 45 和所有数据，其中英里等于 9999。我需要它来做一个或另一个，但不是两者都做。这就是我的桌子的样子

TABLE1                          TABLE2
ID COMPANY MILES ETC            ID COMPANYCODE MILES RATE
1  ILLINI  50                   1  ILLINI      50    3.2
2  ILLINI  110                  2  ILLINI      110   5.2
3  ILLINI  150                  3  ILLINI      150   2.4
4  ILLINI  200                  4  ILLINI      200   1.9
5  ILLINI  250                  5  ILLINI      9999  1.5
6  ILLINI  300                       
7  ILLINI  350
8  ILLINI  400
9  ILLINI  450
10 ILLINI  500

Desired Output
COMPANY MILES MILES2 RATE
ILLINI  50    50    3.2
ILLINI  110   110   5.2
ILLINI  150   150   2.4
ILLINI  200   200   1.9
ILLINI  250   9999  1.5
ILLINI  300   9999  1.5                    
ILLINI  350   9999  1.5
ILLINI  400   9999  1.5
ILLINI  450   9999  1.5
ILLINI  500   9999  1.5

Answer 1

我认为这会给你你想要的：

SELECT t1.COMPANY, t1.MILES,
       CASE WHEN t2.MILES IS NULL THEN t3.MILES
            ELSE t2.MILES
       END AS MILES2,
       CASE WHEN t2.MILES IS NULL THEN t3.RATE
            ELSE t2.RATE
       END AS RATE           
FROM TABLE1 AS t1
LEFT JOIN TABLE2 AS t2 
   ON t1.[COMPANY] = t2.[COMPANYCODE] AND (t1.[MILES] = t2.[MILES])
INNER JOIN (
   SELECT TOP 1 COMPANYCODE, MILES, RATE FROM TABLE2 WHERE MILES = 9999
) AS t3 
   ON t1.[COMPANY] = t3.[COMPANYCODE]    

如果MILES 中有匹配项，则输出包含来自TABLE1、TABLE2 的两条记录。否则，输出包含来自左表的记录，即TABLE1 和来自TABLE2 和MILES = 9999 的特定 记录。

请注意TOP 1 用于最后一个子查询，以防TABLE2 中存在MILES = 9999 的多个记录。

输出：

COMPANY MILES   MILES2  RATE
----------------------------
ILLINI  50      50      3,2
ILLINI  110     110     5,2
ILLINI  150     150     2,4
ILLINI  200     200     1,9
ILLINI  250     9999    1,5
ILLINI  300     9999    1,5
ILLINI  350     9999    1,5
ILLINI  400     9999    1,5
ILLINI  450     9999    1,5
ILLINI  500     9999    1,5

SQL Fiddle Demo here

Answer 2

我会基于双左连接..一次匹配，如果没有，则默认为 9999 实例

SELECT
      T1.*,
      coalesce( T2.miles, T3.miles ) as Miles2,
      coalesce( T2.rate, T3.rate ) as MileageRate
   FROM
      TABLE1 T1
         LEFT JOIN TABLE2 T2
            on T1.Company = T2.CompanyCode
           AND T1.Miles = T2.Miles
         LEFT JOIN TABLE2 T3
            on T1.Company = T3.CompanyCode
           AND T3.Miles = 9999

确认工作at this SQL Fiddle link