TSQL比较两个集合

Question

当给出两组时

s1 = {a,b,c,d} s2 = {b,c,d,a}

(即)

TableA

Item
a
b
c
d

TableB

Item
b
c
d
a

如何编写Sql查询以显示"tableA和tableB中的元素相等".[不使用SP或UDF]

产量

Elements in TableA and TableB contains identical sets

Answer 1

使用:

SELECT CASE 
         WHEN   COUNT(*) = (SELECT COUNT(*) FROM a) 
            AND COUNT(*) = (SELECT COUNT(*) FROM b) THEN 'Elements in TableA and TableB contains identical sets'
         ELSE 'TableA and TableB do NOT contain identical sets'
       END
  FROM (SELECT a.col
          FROM a
        INTERSECT
        SELECT b.col
          FROM b) x 

测试:

WITH a AS (
  SELECT 'a' AS col
  UNION ALL
  SELECT 'b'
  UNION ALL
  SELECT 'c'
  UNION ALL
  SELECT 'd'),
     b AS (
  SELECT 'b' AS col
  UNION ALL
  SELECT 'c'
  UNION ALL
  SELECT 'd'
  UNION ALL
  SELECT 'a')
SELECT CASE 
         WHEN   COUNT(*) = (SELECT COUNT(*) FROM a) 
            AND COUNT(*) = (SELECT COUNT(*) FROM b) THEN 'yes'
         ELSE 'no'
       END
  FROM (SELECT a.col
          FROM a
        INTERSECT
        SELECT b.col
          FROM b) x 

Answer 2

这样的东西,使用FULL JOIN:

SELECT
  CASE 
    WHEN EXISTS (
      SELECT * FROM s1 FULL JOIN s2 ON s1.Item = s2.Item
      WHERE s1.Item IS NULL OR s2.Item IS NULL
      )
    THEN 'Elements in tableA and tableB are not equal'
    ELSE 'Elements in tableA and tableB are equal'
  END

这对第一个非比赛凭借短路,与需要2个每个表的完全扫描其他解决方案(曾经为COUNT(*),一旦加入/ INTERSECT).

估计成本明显低于其他解决方案.