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
);
Related
use the below table 1 to generate table 2
Table 1
Col1 A B C
------------------
N1 1 0 0
N2 0 1 0
N3 1 0 0
Table 2
output
new_col
-------
N1 A
N2 B
N3 A
Also how to use Table 2 to generate table 1 above
Following SQL query can be help to get requested output:
SELECT Col1,IF(A=1,'A',IF(B=1,'B','C')) AS result FROM `table_name`;
You can use conditinal with CONCAT() Function :
SELECT CONCAT(col1,' ',
CASE WHEN A = 1 THEN 'A' ELSE '' END,
CASE WHEN B = 1 THEN 'B' ELSE '' END,
CASE WHEN C = 1 THEN 'C' ELSE '' END)
FROM table1
provided you're on a DBMS with brand name such as MySQL, PostGRES, SQL Server. As an example, Oracle DB won't allow using more than two arguments for CONCAT() Function.
In order to create table2, use for most of the DBMS :
CREATE TABLE table2 AS
SELECT CONCAT(col1,' ',
CASE WHEN A = 1 THEN 'A' ELSE '' END,
CASE WHEN B = 1 THEN 'B' ELSE '' END,
CASE WHEN C = 1 THEN 'C' ELSE '' END) AS new_col
FROM table1
except for SQL Server in which prefer using :
SELECT CONCAT(col1,' ',
CASE WHEN A = 1 THEN 'A' ELSE '' END,
CASE WHEN B = 1 THEN 'B' ELSE '' END,
CASE WHEN C = 1 THEN 'C' ELSE '' END) AS new_col
INTO table2
FROM table1
In order to implement a reverse engineering(go back to original table), you need to consider the dialectics for each seperate database to handle string values. Assume you're using MySQL DB, then consider using :
CREATE TABLE table3 AS
SELECT SUBSTRING(new_col,1,instr(new_col,' ')-1) AS col1,
CASE WHEN instr(new_col,'A') > 0 THEN 1 ELSE 0 END AS A,
CASE WHEN instr(new_col,'B') > 0 THEN 1 ELSE 0 END AS B,
CASE WHEN instr(new_col,'C') > 0 THEN 1 ELSE 0 END AS C
FROM table2
where I used a different table name (table3), since table1 already exists.
Demo
Btw, if Oracle DB is the case, then use :
SELECT CONCAT(CONCAT(col1,' '),
CASE WHEN A = 1 THEN 'A' ELSE '' END||
CASE WHEN B = 1 THEN 'B' ELSE '' END||
CASE WHEN C = 1 THEN 'C' ELSE '' END) AS new_col
FROM table1
You can use one case statement. This works in Oracle.
SELECT col1
|| CASE
WHEN A = 1
THEN 'A'
WHEN B = 1
THEN 'B'
WHEN C = 1
THEN 'C'
END
NEW_COL
FROM table1
It is unclear what you want when there are multiple "1"s in a row. This is a simple solution:
select id, A from t where A = 1
union all
select id, B from t where B = 1
union all
select id, C from t where C = 1;
In databases that support lateral joins, I would recommend:
select t.id, v.which
from t cross join lateral
(values ('A', t.A), ('B', B), ('C', C)
) v(which, val)
where val = 1;
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.
I have a huge query used within a case-when block.
My query looks like this:
SELECT 'TEST' FROM DUAL WHERE 1=1 AND EXISTS(
SELECT
CASE
WHEN EXISTS
(Select 1 from dual where 1=2)
THEN 1
ELSE
(Select 1 from dual where 1=2)
END
FROM DUAL);
I want to execute my select-statement only if the case-when statement returns a record. However, it always prints 'Test' because this code always return a NULL:
SELECT
CASE
WHEN EXISTS
(Select 1 from dual where 1=2)
THEN 1
ELSE
(Select 1 from dual where 1=2)
END
So basically I want to print "TEST" only if no record (or null value) is returned. How can I achieve this?
A row with one column that has a NULL value is not the same as a non-existing row. So, you cannot do exactly what you want using EXISTS. One method is to do:
SELECT 'TEST'
FROM DUAL
WHERE 1 = 1 AND
1 = (SELECT CASE WHEN EXISTS(Select 1 from dual where 1=2)
THEN 1
ELSE 0
END
FROM DUAL
);
That is, look for a particular value, rather than check for the existence of a row.
We can use the following to handle the NULL
CASE TRIM(Your Field) IS NULL
THEN 'The value you want to show/ print'
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
I have three columns in the table MYTABLE (ID, NUM, NAMES). There is a column NAMES. I need to check on NAMES column to see if the first name is JACK or BRUCE and the corresponding NUM column = 0. If the match is found, return 1 else 0.
ID NUM NAMES
1 1 'TOM'
2 1 'MIKE'
3 0 'JACK'
4 1 'MICKY'
5 0 'BRUCE'
I've came up with the following query:
select *
case NAMES in ('JACK', 'BRUCE') and NUM=0 then 1 else 0 end as MYNAMES
from MYTABLE;
That does not work unfortunately.
This works (SQLFiddle demo):
SELECT id, num,
CASE WHEN names IN ('JACK', 'BRUCE') AND num=0
THEN 1 ELSE 0 END AS mynames
FROM mytable
select case
when exists
(
select *
from YourTable
where name in ('JACK', 'BRUCE')
and NUM = 0
)
then 1
else 0
end
from dual
Live example at SQL Fiddle.
select case when NAMES in ('JACK','BRUCE') AND NUM = 0
then 1
else 0
end
from your_table