Sql giao nhau có điều kiện

Question

Tôi muốn biết liệu chúng ta có thể thực hiện giao lộ có điều kiện hay không. theres là somes truy vấn, nhưng kết quả là sai (luôn luôn trống). Tôi viết những gì nó nên kết quả.

DECLARE @CAN_USE_TABLE1 BIT 
DECLARE @CAN_USE_TABLE2 BIT 
DECLARE @CAN_USE_TABLE3 BIT 
DECLARE @CAN_USE_TABLE4 BIT 

DECLARE @TABLE1 AS TABLE (ABC INT) -- values will be 1,2,3 
DECLARE @TABLE2 AS TABLE (ABC INT) -- values will be 1,2 
DECLARE @TABLE3 AS TABLE (ABC INT) --EMPTY TABLE 
DECLARE @TABLE4 AS TABLE (ABC INT) --EMPTY TABLE 
INSERT INTO @TABLE1 VALUES (1) 
INSERT INTO @TABLE1 VALUES (2) 
INSERT INTO @TABLE1 VALUES (3) 
INSERT INTO @TABLE2 VALUES (1) 
INSERT INTO @TABLE2 VALUES (2) 

SET @CAN_USE_TABLE1 = 1 
SET @CAN_USE_TABLE2 = 1 
SET @CAN_USE_TABLE3 = 1 
SET @CAN_USE_TABLE4 = 0 

SELECT ABC FROM @TABLE1 WHERE @CAN_USE_TABLE1 = 1 
INTERSECT 
SELECT ABC FROM @TABLE2 WHERE @CAN_USE_TABLE2 = 1 
INTERSECT 
SELECT ABC FROM @TABLE3 WHERE @CAN_USE_TABLE3 = 1 
INTERSECT 
SELECT ABC FROM @TABLE4 WHERE @CAN_USE_TABLE4 = 1 

--RESULT SHOULD BE : 
-- NO RESULT 
-- 
-- BECAUSE, AT THIS STAGE, TABLE1 AND TABLE2 AND TABLE3 SHOULD BE INTERSECTED. AND BECAUSE TABLE3 IS EMPTY, THE RESULT IS EMPTY. 

SET @CAN_USE_TABLE1 = 1 
SET @CAN_USE_TABLE2 = 1 
SET @CAN_USE_TABLE3 = 0 
SET @CAN_USE_TABLE4 = 0 

SELECT ABC FROM @TABLE1 WHERE @CAN_USE_TABLE1 = 1 
INTERSECT 
SELECT ABC FROM @TABLE2 WHERE @CAN_USE_TABLE2 = 1 
INTERSECT 
SELECT ABC FROM @TABLE3 WHERE @CAN_USE_TABLE3 = 1 
INTERSECT 
SELECT ABC FROM @TABLE4 WHERE @CAN_USE_TABLE4 = 1 

--RESULT SHOULD BE : 
-- 1 
-- 2 
-- 
-- BECAUSE, AT THIS STAGE, TABLE1 AND TABLE2 SHOULD BE INTERSECTED 

SET @CAN_USE_TABLE1 = 0 
SET @CAN_USE_TABLE2 = 1 
SET @CAN_USE_TABLE3 = 0 
SET @CAN_USE_TABLE4 = 0 

SELECT ABC FROM @TABLE1 WHERE @CAN_USE_TABLE1 = 1 
INTERSECT 
SELECT ABC FROM @TABLE2 WHERE @CAN_USE_TABLE2 = 1 
INTERSECT 
SELECT ABC FROM @TABLE3 WHERE @CAN_USE_TABLE3 = 1 
INTERSECT 
SELECT ABC FROM @TABLE4 WHERE @CAN_USE_TABLE4 = 1 

--RESULT SHOULD BE : 
-- 1 
-- 2 
-- 
-- BECAUSE, AT THIS STAGE, ONLY TABLE 2 SHOULD BE USED 

Answer 1

rỗng bộ INTERSECT ed với bất kỳ tập khác sẽ luôn trống. Nó giống như nhân với 0. Bạn luôn có được 0.

Conditional INTERSECT ing sẽ yêu cầu hoặc một truy vấn động, hoặc một bảng dàn dựng, như thế này:

khởi tạo

DECLARE @CAN_USE_TABLE1 BIT 
DECLARE @CAN_USE_TABLE2 BIT 
DECLARE @CAN_USE_TABLE3 BIT 
DECLARE @CAN_USE_TABLE4 BIT 

DECLARE @TABLE1 AS TABLE (ABC INT) 
DECLARE @TABLE2 AS TABLE (ABC INT) 
DECLARE @TABLE3 AS TABLE (ABC INT) 
DECLARE @TABLE4 AS TABLE (ABC INT) 
DECLARE @RESULT AS TABLE (ABC INT) --Adding this result table 
INSERT INTO @TABLE1 VALUES (1) 
INSERT INTO @TABLE1 VALUES (2) 
INSERT INTO @TABLE1 VALUES (3) 
INSERT INTO @TABLE2 VALUES (1) 
INSERT INTO @TABLE2 VALUES (2) 

SET @CAN_USE_TABLE1 = 1 
SET @CAN_USE_TABLE2 = 1 
SET @CAN_USE_TABLE3 = 0 
SET @CAN_USE_TABLE4 = 0 

Processing

INSERT INTO @RESULT 
SELECT ABC FROM @TABLE1 WHERE @CAN_USE_TABLE1=1 UNION 
SELECT ABC FROM @TABLE2 WHERE @CAN_USE_TABLE2=1 UNION 
SELECT ABC FROM @TABLE3 WHERE @CAN_USE_TABLE3=1 UNION 
SELECT ABC FROM @TABLE4 WHERE @CAN_USE_TABLE4=1 

DELETE r FROM @RESULT r 
WHERE NOT EXISTS(SELECT 1 FROM @TABLE1 WHERE ABC=r.ABC) 
AND @CAN_USE_TABLE1=1; 

DELETE r FROM @RESULT r 
WHERE NOT EXISTS(SELECT 1 FROM @TABLE2 WHERE ABC=r.ABC) 
AND @CAN_USE_TABLE2=1; 

DELETE r FROM @RESULT r 
WHERE NOT EXISTS(SELECT 1 FROM @TABLE3 WHERE ABC=r.ABC) 
AND @CAN_USE_TABLE3=1; 

DELETE r FROM @RESULT r 
WHERE NOT EXISTS(SELECT 1 FROM @TABLE4 WHERE ABC=r.ABC) 
AND @CAN_USE_TABLE4=1; 

SELECT * FROM @RESULT; 

quả

1 
2 

Answer 2

declare @sql nvarchar(4000), 
    @params nvarchar(4000) 

if @can_use_table1 = 1 
    select @sql= 'select abc from @table1' 

if @can_use_table2 = 1 
begin 
    if @can_use_table1 = 1 
     select @sql = @sql + ' intersect ' 
    select @sql = @sql + 'select abc from @table2' 
end 

if @can_use_table3 = 1 
begin 
    if @can_use_table1 = 1 or @can_use_table2 = 1 
     select @sql= @sql + ' intersect '   
    select @sql= @sql + 'select abc from @table3' 
end 

if @can_use_table4 = 1 
begin 
    if @can_use_table1 = 1 or @can_use_table2 = 1 or @can_use_table3 = 1 
     select @sql= @sql + ' intersect ' 
    select @sql= @sql + 'select abc from @table4'  
end 

select @params ='@can_use_table1 bit, @can_use_table2 bit, 
     @can_use_table3 bit, @can_use_table4 bit, 
@table1 table, @table2 table, @table3 table, @table4 table' 

exec sp_executesql @sql,@params, 
     @can_use_table1,@can_use_table2, @can_use_table3, @can_use_table4, 
     @table1, @table2, @table3, @table4 

Answer 3

Bạn có thể làm điều này trong một truy vấn như:

select ABC 
from (SELECT ABC, @CAN_USE_TABLE1 as CanUse1, 0 as CanUse2, 0 as CanUse3, 0 as CanUse4 
     FROM @TABLE1 
     union all 
     SELECT ABC, 0, @CAN_USE_TABLE2, 0, 0 FROM @TABLE2 
     union all 
     SELECT ABC, 0, 0, @CAN_USE_TABLE3, 0 FROM @TABLE3 
     union all 
     SELECT ABC, 0, 0, 0, @CAN_USE_TABLE4 FROM @TABLE4 
    ) t 
group by ABC 
having max(Canuse1) = @CAN_USE_TABLE1 AND 
     max(CanUse2) = @CAN_USE_TABLE2 AND 
     max(CanUse3) = @CAN_USE_TABLE3 And 
     max(CanUse4) = @CAN_USE_TABLE4