搜索SQL并返回true或false

Question

I have a table that has thousands of rows in. I need to check if certain values exists in the table or not.

I want to list all the bar codes I am searching with a flag of true or false returned if there is one.

I have come up with this so far:

SELECT CASE WHEN EXISTS (
    SELECT *
    FROM TABLE
    WHERE Coulmn in ('a','b', 'c', 'd', 'e', 'f', 'g')
)
THEN CAST(1 AS BIT)
ELSE CAST(0 AS BIT) END 

This however just returns a value of 1.

So in the table I have

coulmn
----------
A
B
D
E
F
G

I want to do a search that returns the following

Coulmn | Exsists
-----------------
A      |  True
B      |  True
C      |  False
D      |  True
E      |  True
F      |  True
G      |  True

Answer 1

This works:

SELECT *, CASE WHEN (Column in ('1','2')) THEN CAST(1 AS BIT) ELSE CAST(0 AS BIT) END AS result_field
FROM TABLE;

NOTE: Tested in PostgreSQL

Answer 2

You can use a query like the following:

SELECT t1.v,
       CASE WHEN t2.col IS NOT NULL THEN 'true' ELSE 'false' END AS Exists
FROM (
   SELECT 'a' AS v UNION ALL SELECT 'b' UNION ALL SELECT 'c' UNION ALL SELECT 'd'
   UNION ALL SELECT 'e' UNION ALL SELECT 'f' UNION ALL SELECT 'g') AS t1
LEFT JOIN mytable AS t2 ON t1.v = t2.col

Answer 3

As it's written, the outer select is select case when exists () then 1 else 0 end... so it is only going to return one row. The outer select must include "Column" AND "Exists" (select column, ...) to return two columns.

A "where" clause will never return a "false" like this, though, because "column" has to be in a real table for the query to actually return it. As @jarlh says, you'll need a helper table to store the columns you're looking for:

Create table SearchColumns (SearchColumn char(1));
insert into SearchColumns (SearchColumn)
     values ('A'), ('B'), ('C'), ('D'), ('E'), ('F'), ('G'), ('H')

Then you can do the If Exists to your table from that table to see which values are in or not in:

select SearchColumn, case when exists 
    (select * from TABLE where Table.Column = SearchColumns.SearchColumn)
    then 'True' else 'False' end as ExistsStatus
from SearchColumns

I think that will get you what you want. This gets a) Only one record per column no matter how many times it occurs in your table and b) "True" and "False" for every column value you're looking for. If you really wanted a Bit, you can use 0 and 1 and the casting from the original query, but they actually show "0" and "1"; and c) this should work no matter how many values you have.

(Note, I assumed some of those were spelling errors, so I made adjustments, but they were consistent so I'm not certain).

Answer 4

With the help form above I created a temp table and then implemented one of the soultions shared.

CREATE TABLE #Temp
(
       Barcode VARCHAR (100)
)
INSERT INTO #Temp
VALUES
(1),
(2),
(3),
(4 )
select barcode, case when exists 
    (select * from CIPKORHHTProductDetails where CIPKORHHTProductDetails.Barcode = #temp.barcode)
    then 'True' else 'False' end as ExistsStatus
from #temp order by ExistsStatus DESC