I want to write a select query with where clause having two conditions.
select distinct user_name from table1 where column1 = 'AAAA' or is null
I want to give priority to AAAA if records with both AAAA and null are found.
How to do that?
Consider the 'null' entries only if the corresponding AAAA does not exist :
WHERE ... OR (column1 is null AND not exists (select * from table1 as inner where inner.user_name = outer.user_name and inner.column1 = 'AAAA'))
The variation using EXCEPT would be closer to RA-style thinking but would probably fail precisely because you're working with NULL here.
EDIT
(And this answer is only to be kept in mind for the cases where you need more attributes from the row than just the user_name and those attributes must match precisely the row retained for the result set.)
It's just
select distinct user_name from table1 where column1 = 'AAAA' or column1 is null
What do you mean by "if records with both AAAA and null are found." give priority to AAAA"?
One interpretation is to return AAAA records. If none exist, then choose NULL:
select distinct user_name
from table1
where column1 = AAAA
union all
select distinct user_name
from table1
where column1 is null and (not exists select 1 from table1 where column1 = AAAA);
Related
I want to filter the table without the row c
column 1
column 2
a
100
b
200
c
50
null
200
Desired output
column 1
column 2
a
100
b
200
null
200
I tried
select *
from table
where column1 <> 'c'
But since I can compare with null, I'm getting the wrong output. How do I deal with this?
You need to handle the null as follows:
select * from table where column1 <> 'c' or column1 is null
Or you can use the coalesce function as follows:
select * from table where coalesce(column1,'cc') <> 'c'
Coalesce will replace the null value in column1 with the value provided as the second argument. I have used the value which is not equal to 'c' so records with column1 as null will pass this condition
ANSI SQL, DISTINCT predicate.
select *
from table
where column1 is distinct from 'c'
However, not supported by all dbms products.
I have two columns, each with identification numbers that have been brought in from different datasheets.
I want to combine this into one column with both identification numbers if they are different, but only one of the identification numbers if they are the same.
I'm using SELECT DISTINCT CONCAT(column 1, column 2) AS column 3 to combine the columns, but can not filter out UNIQUE combinations.
When I try WHERE column 1 <> column 2, I get an error message.
Any suggestions?
You can use CASE WHEN to test for conditions:
SELECT DISTINCT CASE WHEN column1 = column2 THEN column1
ELSE CONCAT(column1, column2)
END AS column3
FROM table1
try this using IIF or CASE and CONCAT
select
distinct
iif(col1<>col2,concat(col1,col2),col1) [myid]
from mytable
or
select
distinct
case when col1<>col2 then
concat(col1,col2)
else col1 end [myid]
from mytable
You should do something like:
SELECT DISTINCT CASE WHEN column1 = column2 THEN column1
ELSE column1 + '|' + column2
END AS combinedColumn
FROM table1
Consider the following chart:
column1 column2 column1+column2 column1+'|'+column2
12 34 1234 12|34
123 4 1234 123|4
1234 1234 1234 1234
Also, column1+column2 loses some information - what the original parts were.
I have table with 2 col :
UID NAME
-----------
111 AAA
222 BBB
Customer will enter the name and I have to retrieve UID with respective value. If name won't present in the rows, it has to retrieve 000, not like no rows.
I am trying to write query like this:
SELECT
CASE UID
WHEN Count(*) = 0 THEN '000'
ELSE UID
END
FROM table1
WHERE NAME ='XXX'
Please help me in this regard. Thanks in advance...
If UID is an integer, then you need to take casts into account:
select coalesce(cast(max(uid) as char(3)), '000')
from table1
where name = 'XXX'
The cast is intended to be to the type of UID, which seems to be char(3) in your example.
When there are no matching rows, then the max() function returns NULL. The coalesce() turns this into the value you are looking for.
try this
select case
when max(id) is null then
0
else
max(id)
end
from table1
where name = 'b'
You have error in case
SELECT case when count(UID) = 0 THEN '000' ELSE UID end FROM table1 where name = 'XXX'
sqlfiddle :http://www.sqlfiddle.com/#!2/257ea/1
I am constructing an SQL statement with some parameters. Finally, an SQL statement is created like
"select * from table where column1 = "xyz"".
But I also need the rows which are filtered with this statement. In this case they're rows which are not "xyz" valued in column1. More specifically, I am looking for something like INVERSE(select * from table where ...). Is it possible?
Edit: My bad, I know I can do it with != or operator. Here the case is, select statement may be more complex (with some ANDs and equal, greater operators). Let's assume a table has A,B,C and my SQL statement brings only A as result. But I need B and C while I only have the statement which brings A.
select * from table where column1 != 'xyz' or column1 is null;
If you want the other ones, do it like this:
select * from table where column1 <> "xyz"
column1 <> (differs from) "xyz"
To check if something is no equal you can use <> or even !=
SELECT *
FROM yourTable
WHERE <> 'xyz'
OR
SELECT *
FROM yourTable
WHERE != 'xyz'
Many database vendors support (see list) both versions of the syntax.
If you're retrieving both result sets at about the same time, and just want to process the xyz ones first, you could do:
select *,CASE WHEN column1 = "xyz" THEN 1 ELSE 0 END as xyz from table
order by CASE WHEN column1 = "xyz" THEN 1 ELSE 0 END desc
This will return all of the rows in one result set. Whilst xyz = 1, these were the rows with column1 = 'xyz'.
It was :
"select * from table where rowId NOT IN (select rowId from table where column1 = "xyz")
I needed a unique rowId column to achieve this.
I want to be able to compare 2 records in the same SQL table and tell if they are different. I do not need to tell what is different, just that they are different.
Also, I only need to compare 7 of 10 columns in the records. ie.) each record has 10 columns but I only care about 7 of these columns.
Can this be done through SQL or should I get the records in C# and hash them to see if they are different values?
You can write a group by query like this:
SELECT field1, field2, field3, .... field7, COUNT(*)
FROM table
[WHERE primary_key = key1 OR primary_key = key2]
GROUP BY field1, field2, field3, .... field7
HAVING COUNT(*) > 1
That way you get all records with same values for field 1 to 7, along with the number of occurrences.
Add the part between brackets to limit your search for duplicates, either with OR, or with IN (...).
IF EXISTS (SELECT Col1, Col2, ColEtc...
from MyTable
where condition1
EXCEPT SELECT Col1, Col2, ColEtc...
from MyTable
where condition2)
BEGIN
-- Query returns all rows from first set that are not column for column
-- also in the second (EXCEPT) set. So if there are any, there will be
-- rows returned, which meets the EXISTS criteria. Since you're only
-- checking EXISTS, SQL doesn't actually need to return columns.
END
No hash is necessary. Normal equality comparison is enough:
select isEqual = case when t1.a <> t2.a or t1.b <> t2.b bbb then 1 else 0 end
SELECT
CASE WHEN (a.column1, a.column2, ..., a.column7)
= (b.column1, b.column2, ..., b.column7)
THEN 'all 7 columns same'
ELSE 'one or more of the 7 columns differ'
END AS result
FROM tableX AS a
JOIN tableX AS b
ON t1.PK = #PK_of_row_one
AND t2.PK = #PK_of_row_two
Can't you just use the DISTINCT keyword? All duplicates will not be returned, so each row you receive is unique (and different from the others).
http://www.mysqlfaqs.net/mysql-faqs/SQL-Statements/Select-Statement/How-does-DISTINCT-work-in-MySQL
So you could make this query:
SELECT DISTINCT x,y,z FROM RandomTable WHERE x = something
Which will only return one row for each unique x,y,z combination.