I have a huge query and I am wondering if it is in Oracle possible
to get the result of a case-when-statement and use it for comparison? My CASE-STATEMENT is declared in the Select-Statement and it looks like this.
SELECT........
(CASE
WHEN (Select 1 from DUAL) = 1 THEN 'TEST'
ELSE 'TEST2'
END) AS TEST;
Now I want to get the result of this case-statement and use it in the where part? Is it possible? (Sry this may be a dumb question)
If you define your CASE statement in either an inline-view or a common table expression (aka WITH clause), you can refer to it by whatever alias you give it.
For example (inline-view):
SELECT ...
FROM ( SELECT .....
(CASE
WHEN (Select 1 from DUAL) = 1 THEN 'TEST'
ELSE 'TEST2'
END) AS TEST
FROM...
) v
WHERE v.test = 'TEST2';
As a common table expression, it would be:
WITH cte AS ( SELECT........
(CASE
WHEN (Select 1 from DUAL) = 1 THEN 'TEST'
ELSE 'TEST2'
END) AS TEST
FROM ... )
SELECT ...
FROM cte
WHERE test = 'TEST2';
You can use a case statement in the where clause, for eg.:
select * from table
where table.field = (CASE
WHEN (Select 1 from DUAL) = 1 THEN 'TEST'
ELSE 'TEST2'
END)
This will compare the value returned from the case statement with the table field.
Related
I want to check conditions in query. If condition is false, then query must returns error code, else query must to execute another query.
Something like that:
WITH error_code_get AS (
SELECT
CASE
WHEN NOT EXISTS (
SELECT 1
FROM users
WHERE id = '1a4b...'
) THEN 1
WHEN NOT EXISTS (
SELECT 1
FROM workspaces
WHERE id = '353...'
) THEN 2
WHEN (
SELECT settings
FROM workspace_roles
WHERE workspace_id = '353...'
AND id IN (
SELECT role_id
FROM m2m_users_to_workspace_or_projects_roles
WHERE role_type='1'
AND user_id='1a4b...'
)
) < 2 THEN 3
ELSE 0
END error_code
RETURNING error_code
)
// WRONG PART
CASE
WHEN (SELECT error_code FROM error_code_get) = 0 THEN (INSERT INTO x(a) VALUES('some_value'))
ELSE (SELECT error_code FROM error_code_get)
END
You can't do something like that in pure SQL, you'd need to write code in Stored Proc or Function
I am trying to select different values that depend on different conditions, but I don't exactly know, how one can achieve this in SQL/Oracle..
Here is an example:
SELECT VALUE (I dont exactly know what to write here)
FROM
(SELECT
(CASE
WHEN (Select 1 from DUAL) = 1 THEN 'TEST'
WHEN (Select 1 from DUAL) = 0 THEN 'TEST1'
WHEN (Select 1 from DUAL) = 0 THEN 'TEST2'
ELSE 'N/A'
END)
FROM DUAL);
I want to print different results according to the conditions...For instance, in the example above it should print "TEST"
You need to provide an alias to the CASE statement:
SELECT alias_for_your_case_value
FROM (
SELECT CASE (Select 1 from DUAL)
WHEN 1 THEN 'TEST'
WHEN 0 THEN 'TEST1'
WHEN 0 THEN 'TEST2'
ELSE 'N/A'
END AS alias_for_your_case_value
FROM DUAL
);
I'm trying to do something similar to this:
CASE
WHEN number IN (1,2,3) THEN 'Y' ELSE 'N' END;
Instead I want to have a query in the place of the list, like so:
CASE
WHEN number IN (SELECT num_val FROM some_table) THEN 'Y' ELSE 'N' END;
I can't seem to get this to work. Also, here is an example of the query.
SELECT number, (CASE
WHEN number IN (SELECT num_val FROM some_table) THEN 'Y' ELSE 'N' END) AS YES_NO
FROM some_other_table;
Yes, it's possible. See an example below that would do what you are intending. The difference is that it uses EXISTS instead of IN.
SELECT a.number,
(CASE WHEN EXISTS (SELECT null FROM some_table b where b.num_val = a.number)
THEN 'Y'
ELSE 'N'
END) AS YES_NO
FROM some_other_table a;
EDIT:
I confess: I like the answers given by the others better personally.
However, there will be a difference between this query and the others depending on your data.
If for a value number in the table some_other_table you can have many matching entries of num_val in the table some_table, then the other answers will return duplicate rows. This query will not.
That said, if you take the left join queries given by the others, and add a group by, then you won't get the duplicates.
I suggest using an OUTER JOIN instead of trying to use a subquery in a CASE expression:
SELECT t.NUMBER,
CASE
WHEN s.NUM_VAL IS NOT NULL THEN 'Y'
ELSE 'N'
END AS YES_NO
FROM SOME_OTHER_TABLE t
LEFT OUTER JOIN SOME_TABLE s
ON s.NUM_VAL = t.NUMBER
Best of luck.
Seems like you just need to join the tables and do a decode.
with x as
(
select 1 as num from dual
union
select 2 as num from dual
union
select 3 as num from dual
),
y as
(
select 1 as num from dual
union
select 2 as num from dual
union
select 4 as num from dual
)
select x.num, decode(y.num, null, 'N','Y') as yes_no
from x
left outer join y on (x.num = y.num)
Output:
NUM YES_NO
1 Y
2 Y
3 N
You can use subquery in case statement:
select
case dummy
when 'X' then (select 'TRUE' from dual)
else 'FALSE'
end TEST
from dual;
TEST
TRUE
select
case (select 'XXX' from dual)
when 'XXX' then 'TRUE'
else 'FALSE'
end TEST
from dual;
TEST
TRUE
What is the equivalent of the below SQL Query in Oracle?
SELECT CAST(
CASE WHEN EXISTS(SELECT * FROM theTable where theColumn like 'theValue%') THEN 1
ELSE 0
END
AS BIT)
I just want an oracle query where exists is used and it returns 0 or 1 like above.
The equivalent would be:
select count(*)
from dual
where exists (SELECT * FROM theTable where theColumn like 'theValue%')
This would show the same output. Just removed the CAST and added a FROM dual as Oracle doesn't allow queries with SELECT and without FROM:
SELECT
CASE WHEN EXISTS(SELECT * FROM theTable where theColumn like 'theValue%')
THEN 1
ELSE 0
END
FROM dual ;
Tested at SQL-Fiddle
You could write it:
SELECT COUNT(*) FROM theTable WHERE theColumn LIKE 'theValue%' AND ROWNUM = 1
This will return 0-1 and the optimizer gets that the query is to be optimized for first-row access.
You could also use MAX with CASE:
SELECT MAX(
CASE
WHEN theColumn like 'theValue%' THEN 1
ELSE
0
END)
AS BIT
FROM theTable
You can use one of the following queries: (the first ones is more performant)
SELECT H.TABLE_ID, H.OTHER_FIELD,
(SELECT 'YES' FROM DUAL WHERE EXISTS (SELECT 'X' FROM TABLE_DETAIL DT
WHERE DT.TABLE_ID = H.TABLE_ID) ) WITH_DETAIL FROM TABLE_HEADER H;
SELECT H.TABLE_ID, H.OTHER_FIELD,
CASE WHEN EXISTS(SELECT * FROM IMTS.DETAIL_TABLE DT WHERE DT.TABLE_ID=H.TABLE_ID)
THEN 'Y' ELSE 'N' END WITH_DETAIL FROM HEADER_TABLE H;
SELECT H.TABLE_ID, H.OTHER_FIELD, NVL2(DT.SOME_NOTNULL_FIELD, 'YES','NO') WITH_DETAIL
FROM TABLE_HEADER H
LEFT JOIN TABLE_DETAIL DT ON DT.TABLE_ID=H.TABLE_ID AND ROWNUM<2;
Is it possible to alias a column name and then use that in a CASE statement? For example,
SELECT col1 as a, CASE WHEN a = 'test' THEN 'yes' END as value FROM table;
I am trying to alias the column because actually my CASE statement would be generated programmatically, and I want the column that the case statement uses to be specified in the SQL instead of having to pass another parameter to the program.
This:
SELECT col1 as a,
CASE WHEN a = 'test' THEN 'yes' END as value
FROM table;
...will not work. This will:
SELECT CASE WHEN a = 'test' THEN 'yes' END as value
FROM (SELECT col1 AS a
FROM TABLE)
Why you wouldn't use:
SELECT t.col1 as a,
CASE WHEN t.col1 = 'test' THEN 'yes' END as value
FROM TABLE t;
...I don't know.
I think that MySql and MsSql won't allow this because they will try to find all columns in the CASE clause as columns of the tables in the WHERE clause.
I don't know what DBMS you are talking about, but I guess you could do something like this in any DBMS:
SELECT *, CASE WHEN a = 'test' THEN 'yes' END as value FROM (
SELECT col1 as a FROM table
) q
#OMG Ponies - One of my reasons of not using the following code
SELECT t.col1 as a,
CASE WHEN t.col1 = 'test' THEN 'yes' END as value
FROM TABLE t;
can be that the t.col1 is not an actual column in the table. For example, it can be a value from a XML column like
Select XMLColumnName.value('(XMLPathOfTag)[1]', 'varchar(max)')
as XMLTagAlias from Table
It should work. Try this
Select * from
(select col1, col2, case when 1=1 then 'ok' end as alias_col
from table)
as tmp_table
order by
case when #sortBy = 1 then tmp_table.alias_col end asc
I use CTEs to help compose complicated SQL queries but not all RDBMS' support them. You can think of them as query scope views. Here is an example in t-sql on SQL server.
With localView1 as (
select c1,
c2,
c3,
c4,
((c2-c4)*(3))+c1 as "complex"
from realTable1)
, localView2 as (
select case complex WHEN 0 THEN 'Empty' ELSE 'Not Empty' end as formula1,
complex * complex as formula2
from localView1)
select *
from localView2
Nor in MsSql
SELECT col1 AS o, e = CASE WHEN o < GETDATE() THEN o ELSE GETDATE() END
FROM Table1
Returns:
Msg 207, Level 16, State 3, Line 1
Invalid column name 'o'.
Msg 207, Level 16, State 3, Line 1
Invalid column name 'o'.
However if I change to CASE WHEN col1... THEN col1 it works
If you write only equal condition just:
Select Case columns1 When 0 then 'Value1'
when 1 then 'Value2' else 'Unknown' End
If you want to write greater , Less then or equal you must do like this:
Select Case When [ColumnsName] >0 then 'value1' When [ColumnsName]=0 Or [ColumnsName]<0 then
'value2'
Else
'Unkownvalue' End
From tablename
Thanks
Mr.Buntha Khin
SELECT
a AS [blabla a],
b [blabla b],
CASE c
WHEN 1 THEN 'aaa'
WHEN 2 THEN 'bbb'
ELSE 'unknown'
END AS [my alias],
d AS [blabla d]
FROM mytable
Not in MySQL. I tried it and I get the following error:
ERROR 1054 (42S22): Unknown column 'a' in 'field list'
In MySql, alice name may not work, therefore put the original column name in the CASE statement
SELECT col1 as a, CASE WHEN col1 = 'test' THEN 'yes' END as value FROM table;
Sometimes above query also may return error, I don`t know why (I faced this problem in my two different development machine). Therefore put the CASE statement into the "(...)" as below:
SELECT col1 as a, (CASE WHEN col1 = 'test' THEN 'yes' END) as value FROM table;
Yes, you just need to add a parenthesis :
SELECT col1 as a, (CASE WHEN a = 'test' THEN 'yes' END) as value FROM table;
make it so easy.
select columnnameshow = (CASE tipoventa
when 'CONTADO' then 'contadito'
when 'CREDITO' then 'cred'
else 'no result'
end) from Promocion.Promocion