I have a scenario where I have to search value of column 1 in first table to see whether it matches some value in another table.
This should continue in a loop until the last row on first table has been compared.
No loops needed. You can do this easily as a set based operation using exists()
select *
from FirstTable
where exists (
select 1
from SecondTable
where FirstTable.Column1 = SecondTable.Column1
);
To find the opposite, where the row in the first table does not have a match based on Column1, you can use not exists()
select *
from FirstTable
where not exists (
select 1
from SecondTable
where FirstTable.Column1 = SecondTable.Column1
);
If you want to identify which rows have a match and don't you can use:
select FirstTable.*
, MatchFound = case when x.Column1 is null then 'No' else 'Yes' end
, x.Column1
from FirstTable
outer apply (
select top 1
*
from SecondTable
where FirstTable.Column1 = SecondTable.Column1
) as x
Related
Below is the table from which I need to create conditionalize view.
and I am getting one flag from different table. So based on the flag values i.e. if flag=1 then I need to display actual column values from table, and if flag=0 then show all column values as null values.
I know we can handle it using CASE statement but here, in may case column count is very big so need to handle it in better way.
You could try using a CASE expression along with REGEXP_REPLACE to mask the value column:
SELECT ID,
CASE WHEN flag = 1 THEN Value ELSE REGEXP_REPLACE(Value, '.', '*') END AS Value
FROM yourTable;
You can use left join:
select t.*
from (select 1 as flag from dual) x left join
t
on x.flag = :flag;
If :flag = 1, then all columns will be shown. If :flag is anything else, then all values will be NULL.
If you actually want to show the ids, it is a little more complicated:
select i.*, t.*
from (select 1 as flag from dual) x left join
(select id, . . . -- columns you want to keep
from t
) i left join
t
on x.flag = :flag and t.id = i.id;
You will probably need to list out the columns with the NULL values.
I have two queries, first is a check if value exists in table1, if yes - I'm updating a value in table2, otherwise I return 0 as a count of found values.
It happens really often and I wish I could do that with one query. How would the query look like then?
Maybe you can try something like this. A RETURNING clause will return rows if at least one row was updated in the with clause. It is then verified by an exists check in the select part.
with upd as
(
update table2 t2 set col = 'value4'
where id = ? and exists ( select 1 from table1 t1 where id = ? ) returning *
)
select exists ( select 1 from upd ) :: int as "updated";
This query when run will return 0 ( integer equivalent of boolean false ) when no rows exist and 1 when at least one row was updated.
DEMO
You can join table1 & table2 and then update the value from table2 with table1.
I have to create a new table and inside should be the columns I get from the CASE statement. I do not need the rest of the columns resulting from the select statement
for example:
CREATE TABLE test
AS (
SELECT a.id, ...
CASE WHEN a.id = 1 THEN 2
ELSE 0
END as LegalType
FROM table a, ...
WHERE ...);
now my question how can I select only the column LegalType from the CASE statement? I do not want to have column a.id
You can SELECT INTO
SELECT CASE WHEN a.id = 1 THEN 2 ELSE 0 END as LegalType
....
INTO test
FROM table a
WHERE 1=1);
This will create you a table based on the data returned in the SELECT. see https://msdn.microsoft.com/en-GB/library/ms188029.aspx
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
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
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
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).
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
I have a sub query that returns one column, showing as GroupType, I then want to do a CASE function on this result within the main query, however I get an invalid column name when using the CASE statement.
Can i do this in SQL to do I have to refer to it by a different name
SELECT CASE
WHEN
(
SELECT column
FROM othertable
) = 1
THEN '1'
ELSE '2'
END
FROM mytable
To reuse the subquery result:
SELECT subvalue, CASE subvalue WHEN 1 THEN 1 ELSE 2 END
FROM (
SELECT (
SELECT column
FROM othertable
) AS subvalue
FROM mytable
) q