如何从同一张表中组合三个“选择不同”

Question

对于一个搜索功能，我想返回三种类型的结果，所以我查询了3次。将查询 JOIN 或 UNION 合并为一个可能会更好，但是如何..

string sql1 = "SELECT DISTINCT area, CHARINDEX(@ss, area) FROM rgmaplocation WHERE area LIKE '%' + @ss + '%' ORDER BY CHARINDEX(@ss, area) ";
string sql2 = "SELECT DISTINCT compound, CHARINDEX(@ss, compound) FROM rgmaplocation WHERE compound LIKE '%' + @ss + '%' ORDER BY CHARINDEX(@ss, compound) ";
string sql3 = "SELECT DISTINCT streetname, CHARINDEX(@ss, streetname) FROM rgmaplocation WHERE streetname LIKE '%' + @ss + '%' ORDER BY CHARINDEX(@ss, streetname)";

Answer 1

类似这样的东西来合并结果并按 charindex 表达式进行排序。

;WITH C(Loc, Idx) AS
(
  SELECT DISTINCT area, CHARINDEX('g', area) 
  FROM rgmaplocation 
  WHERE area LIKE '%g%' 
  UNION ALL
  SELECT DISTINCT compound, CHARINDEX('g', compound) 
  FROM rgmaplocation 
  WHERE compound LIKE '%g%' 
  UNION ALL
  SELECT DISTINCT streetname, CHARINDEX('g', streetname) 
  FROM rgmaplocation 
  WHERE streetname LIKE '%g%' 
)
SELECT Loc, Idx
FROM C
ORDER BY Idx

Answer 2

Mikael Eriksson's solution 如果您不介意将区域、小区和街道名称混在一起，那就太好了。如果你想把它们分开，你去吧

WITH C(No,Loc, Idx) AS
(
  SELECT DISTINCT 1,area, CHARINDEX('g', area) 
  FROM rgmaplocation 
  WHERE area LIKE '%g%' 
  UNION 
  SELECT DISTINCT 2,compound, CHARINDEX('g', compound) 
  FROM rgmaplocation 
  WHERE compound LIKE '%g%' 
  UNION 
  SELECT DISTINCT 3,streetname, CHARINDEX('g', streetname) 
  FROM rgmaplocation 
  WHERE streetname LIKE '%g%' 
)
SELECT No,Loc, Idx
FROM C
ORDER BY No,Idx

Answer 3

使用UNION，就像你说的那样：

string sqlAll = string.Format( "{0} UNION {1} UNION {2}", sql1, sql2, sql3 );