How can I quickly check to see if the data from the test table 'test_table', and selected columns are unique and not null.
Summary, at the entrance gets a table name and a list of columns in the output are expected , eg . flag 1 or 0.
Table is big so unfortunately i must posibly fast execute;
select 1 from dual
where exsist (select col1,col2,col3,... from table
where col1 is not null and col2 is not null and col3....
group by col1,col2,col3.. having count(*) > 1 )
this will return 1 when one of the is true.
SELECT 1
FROM dual
WHERE EXISTS
(SELECT a, b FROM tab WHERE id=1
AND name='John'
AND (a IS NULL OR b IS NULL))
I changed your code and I have one question about it , now I have is that id must be 1 and the name 'John ' and any of verifying null must be correct, and wants to have that must be id = 1 and the name 'John ' and if there is either the value of the column is ' null'
Related
Are there other special literal values besides NULL in SQL / PostgresQL?
NULL is nice in that we can interpret NULL as the concept of "nothing" (i.e. missing, not available, not asked, not answered, etc.), and data columns of any type can have NULL values.
I would like another value that I can interpret as representing another concept (here the idea of "everything"), in the same result set.
Is there another special value that I can return in a query, which like NULL doesn't type conflict?
Basically anything that doesn't throw ERROR: For 'UNION', types varchar and numeric are inconsistent in this toy query:
select 1 as numeral, 'one' as name UNION ALL
select 2 as numeral, 'two' as name UNION ALL
select NULL as numeral, NULL as name UNION ALL
select -999 as numeral, -999 as name UNION ALL -- type conflict
select '?' as numeral, 'x' as name -- type conflict
Here,
-999 doesn't work as its type conflicts with varchar columns
'~' doesn't work as its type conflicts with numeric columns
NULL doesn't work as it needs
More specifically here's my actual case, counting combinations of values and also include "Overall" rows in the same query. Generally I won't know or control the types of columns A, B, C in advance. And A, B, or C might also have NULL values which I would would still want to count separately.
SELECT A, COUNT(*) FROM table GROUP BY 1
UNION ALL
SELECT ?, COUNT(*) FROM table GROUP BY 1
and get a result set like:
A
COUNT
NULL
2
1
3
2
5
3
10
(all)
20
SELECT B, COUNT(*) FROM table GROUP BY 1
UNION ALL
SELECT ?, COUNT(*) FROM table GROUP BY 1
and get a result set like:
B
COUNT
NULL
2
'Circle'
3
'Line'
5
'Triangle'
10
(all)
20
You can use function CAST to convert the format to VARCHAR to be considered as string.
NOTE: Thanks to the comments above, I should completely rephrase this question as "How to COUNT/GROUP BY with ROLLUP using multiple columns of mixed/arbitrary/unknown types, and differentiate true NULL values from ROLLUP placeholders?"
The correct answer I believe is provided by #a_horse_with_no_name: use ROLLUP with GROUPING.
Below is is just me drafting that more completely with a revised example:
This toy example has an integer and a string
WITH table AS (
select 1 as numeral, 'one' as name UNION ALL
select 2 as numeral, 'two' as name UNION ALL
select 2 as numeral, 'two' as name UNION ALL
select NULL as numeral, NULL as name UNION ALL
select NULL as numeral, NULL as name UNION ALL
select NULL as numeral, NULL as name
)
select name, numeral, COUNT(*), GROUPING_ID()
FROM table
GROUP BY ROLLUP(1,2)
ORDER BY GROUPING_ID, name, numeral ;
It returns the following result:
numeral
name
count
grouping_id
note
NULL
NULL
3
0
both are true NULLs as grouping is 0
1
one
1
0
2
two
2
0
NULL
NULL
3
1
first is a true NULL, second is a ROLLUP
1
NULL
1
1
2
NULL
2
1
NULL
NULL
6
3
both NULLs are ROLLUPs
I have table A which contains 5 columns col1 to col5.totally it contains 6 rows.I am using DB2 sql
Below is the data for col2.
A
A
test
testasfdla
Null
Null
Requirement:-
If col2 contains null i need assign sequence number starting with 1.
excepted o/p:-
Below is the data for col2.
A
A
test
testasfdla
1
2
I tried with row_number but did not get the required o/p.
Try this:
WITH T (C) AS
(
VALUES
'A'
, 'A'
, 'test'
, 'testasfdla'
, Null
, Null
)
SELECT COALESCE(C, TO_CHAR(ROW_NUMBER() OVER (PARTITION BY C)))
FROM T
I have a table with data
|FormID|Name|
1 A
1 B
2 A
2 C
3 B
3 C
I am trying to query all rows where Name 'A' appears, however i also want to get all rows with the same FormID when the name occurs
For example
Select * from table where name = 'A'
resultset
|FormID|Name|
1 A
2 A
1 B
2 C
Right now i am just querying for the FormID values where the name occurs and then doing another query with the FormID number (Select * from table where formID in (1,2) ) but there must be a way to do this in one sql statement
You can use exists:
select t.*
from t
where t.name = 'A' or
exists (select 1
from t t2
where t2.formid = t.formid and t2.name = 'A'
);
Actually, the first condition is not necessary, so this suffices:
select t.*
from t
where exists (select 1
from t t2
where t2.formid = t.formid and t2.name = 'A'
);
Another approach:
SELECT formid, name
FROM forms
WHERE formid IN (SELECT formid FROM forms WHERE name = 'A')
ORDER BY name;
gives
formid name
---------- ----------
1 A
2 A
1 B
2 C
Because the subquery in the IN doesn't depend on the current row being looked at, it only has to be evaluated once, making it more potentially more efficient for large tables.
Here is the query
select col1
from table
col1 contains these category values:
A
B
C
NULL
How can I rename null category to D?
If you want to make the change permanent
UPDATE table
SET col1 = 'D'
WHERE col1 IS NULL
From then on you can simply query with ...
SELECT col1
FROM table
... to get the desired result.
If there is more than one row having a NULL in col1, you need to filter by a unique key, preferably by the primary key (which every table should have by the way). Let's say you have a table like
id (PK) col1
--- ----
1 'A'
2 'B'
3 'C'
4 NULL
5 NULL
then you can fix it with
UPDATE table SET col1 = 'D' WHERE id = 4;
UPDATE table SET col1 = 'E' WHERE id = 5;
unless you can calculate the new value from another column, e.g.:
UPDATE table
SET col1 = UPPER(LEFT(name, 1))
Try this : ISNULL( ) function is used to replace NULL value with another value
select isnull(col1,'D') as col1
from table
SQL Server uses ISNULL().
SELECT ISNULL(value_to_check, use_this_instead_if_valuetocheck_is_null)
For your code:
select ISNULL(col1, 'D') AS col_name
from table
However, this will happen across the board for this column. You can't use this to make a sequence, like D then E then F. Any NULL value you come across in this column will change to D.
I have a table where the id field (not a primary key) contains either 1 or null. Over the past several years, any given part could have been entered multiple times with one, or both of these possible options.
I'm trying to write a statement that will return some value if there is ever a 1 associated with the select statement. There are lots of semi-duplicate rows, some with 1 and some with null, but if there is ever a 1, I want to return true, and if there are only null values, I want to return false. I'm not sure how to code this though.
If this is my SELECT part,id from table where part = "ABC1234" statement
part id
ABC1234 1
ABC1234 null
ABC1234 null
ABC1234 null
ABC1234 1
I want to write a statement that returns true, because 1 exists in at least one of these rows.
The closest I've come to this is by using a CASE statement, but I'm not quite there yet:
SELECT
a1.part part,
CASE WHEN a2.id is not null
THEN
'true'
ELSE
'false'
END AS id
from table.parts a1, table.ids a2 where a1.part = "ABC1234" and a1.key = a2.key;
I also tried the following case:
CASE WHEN exists
(SELECT id from table.ids where id = 1)
THEN
but I got the error subqueries are not supported in the select list
For the above SELECT statement, how do I return 1 single line that reads:
part id
ABC1234 true
You can use conditional aggregation to check if a part has atleast one row with id=1.
SELECT part,'True' id
from parts
group by part
having count(case when id = 1 then 1 end) >= 1
To return false when the id's are all nulls use
select part, case when id_true>=1 then 'True'
when id_false>=1 and id_true=0 then 'False' end id
from (
SELECT part,
count(case when id = 1 then 1 end) id_true,
count(case when id is null then 1 end) id_false,
from parts
group by part) t