In the below table, I want to write a SQL query to exclude a row when col1=2 and col2=1. Only when both conditions are met, I want to drop that column. If col1=2 but col2<>1 then I want to keep that row.
col1
col2
1
2
1
2
2
2
2
1
I am trying this below snippet but it's not working:
select *
from table
where (col1<>2 and col2<>1)
You can use either:
WHERE NOT (col1 <> 2 AND col2 <> 1)
or
WHERE (col1 <> 2 OR col2 <> 1)
You should use or instead of and.
Related
Let's say I have a table like this:
test
Col1
Col2
A
1
B
1
C
1
D
2
I am doing query select col1 from test where col2 = 1;
This will return a column with values A B and C in 3 separate rows.
I want the SQL to return a single row with value A|B|C. Is this possible to do? If it is how should I do it?
you can use LISTAGG function like this:
SELECT LISTAGG(col1, ',')
If LISTAGG is not available, it can be reproduced with XMLAGG:
SELECT SUBSTR(XMLSERIALIZE(XMLAGG(XMLTEXT('|'||"Col1"))),2)
FROM "test"
WHERE "Col2" = 1
When I try to join the below two table
I am not able to get the output I want by the join.
I tried using join but it didn't work let me know if its possible with plsql
Table 1:
col1 col2
1 a
1 b
1 c
2 a
2 b
3 a
table 2:
col1 col2
1 x
1 y
2 x
2 y
3 x
3 y
The output must be:
col1 col2 col3
1 a x
1 b y
1 c
2 a x
2 b y
3 a x
3 y
If use the join I am not able to get the same output as above.
The output I am getting is
1 a x
1 a y
1 b x
1 b y
1 c x
1 c y
2 a x
.....
.....
3 a x
3 a y
What you are searching is called a FULL OUTER JOIN. The result of this join contains elements from both input-tables, matching records get combined.
You can find more information here: https://stackoverflow.com/questions/4796872/full-outer-join-in-mysql
Using Window functions, specifically ROW_NUMBER() and partitioning by the Col1 in both tables, we can get a partitioned row_number that can be used as part of the join.
In other words, it seems to me that the order that the records are in is crucial for the join and result set you are desiring. Furthermore, using #Benvorth's suggestion of a FULL OUTER JOIN to achieve the NULLs in both direction.. I believe this might work:
SELECT
COALESCE(t1.col1,t2.col1) as col1,
t1.col2,
t2.col2
FROM
(SELECT col1, col2, ROW_NUMBER() OVER (PARTITION BY col1 ORDER BY col2 ASC) as col1_row_number FROM table1) t1
FULL OUTER JOIN
(SELECT col1, col2, ROW_NUMBER() OVER (PARTITION BY col1 ORDER BY col2 ASC) as col1_row_number FROM table2) t2 ON
t1.col1 = t2.col1 AND
t1.col1_row_number = t2.col1_row_number
That ROW_NUMBER() OVER (PARTITION BY col1, ORDER BY col2 ASC) bit will create row number for each record. The row_number will restart back at 1 for each new col1 value encountered. You can think of it like a RANK for each distinct Col1 value based on Col2's value. Table1's output from the subquery SELECT col1, col2, ROW_NUMBER() OVER (PARTITION BY col1 ORDER BY col2 ASC) as col1_row_number FROM table1 will look like:
Table 1:
col1 col2 col1_row_number
1 a 1
1 b 2
1 c 3
2 a 1
2 b 2
3 a 1
So we do that with both tables, then we use that row number as part of the join along with col1.
A sqlfiddle showing this matching your desired result from the question
I want a function or a trigger that when a row is inserted that all rows with matching criteria are given a random integer between 1 and the number of rows so to randomise the rows on a select.
E.g. if I have the data
Col1 Col2 Order
A 1
B 2
B 2
B 3
A 2
and I insert another row with Col1=B and Col2=2 then I want to end up with
Col1 Col2 Order
A 1
B 2 2
B 2 3
B 3
A 2
B 2 1
Where Order is a number with a value of 1 - with each number appearing only once?
There is no need to store this, you can generate such a number when you retrieve the data.
select col1,
col2,
row_number() over (partition by col1, col2 order by random()) as random_order
from the_table
Suppose I have a table as follows: (on DB2 9.7.2)
COL1 COL2 COL3
----------- ---------- ----------
3 4 xyz
3 4 xyz
Now I want to write a query such that only one from these two identical records will be deleted. How can I achieve this?
I can think of :
delete from ;
or
delete from where col1=3;
but both of the above queries will delete both records whereas I want to keep one of them.
If LIMIT doesn't work, this will:
DELETE FROM (SELECT * FROM tbl WHERE col = 3 FETCH FIRST ROW ONLY)
Can't you use a limit clause?
DELETE FROM <table> WHERE <column>=3 LIMIT 1
This is something that served my purpose:
DELETE FROM tabA M
WHERE M.tabAky IN (SELECT tabAky
FROM (SELECT tabAky,
ROW_NUMBER() OVER (PARTITION BY tabAcol1,
tabAcol2,
tabAcoln)
FROM tabA a) AS X (tabAky, ROWNUM)
WHERE ROWNUM> 1) ;
Try This
delete from table A (select row_number() over (partition by col1 order by col1 ) count,* from table) where A.count> 1
I've this table
col 1 col 2 col 3 .... col N
-------------------------------------
1 A B fooa
10 A foo cc
4 A B fooa
it is possible with a tsql query to return only one row with a value only where the values are ALL the same?
col 1 col 2 col 3 .... col N
-------------------------------------
-- A -- --
SELECT
CASE WHEN COUNT(col1) = COUNT(*) AND MIN(col1) = MAX(col1) THEN MIN(col1) END AS col1,
CASE WHEN COUNT(col2) = COUNT(*) AND MIN(col2) = MAX(col2) THEN MIN(col2) END AS col2,
...
FROM yourtable
You have to allow for NULLs in the column:
COUNT(*) counts them
COUNT(col1) doesn't count them
That is, a columns with a mix of As and NULLs isn't one value. MIN and MAX would both give A because they ignore NULLs.
Edit:
removed DISTINCT to get counts the same for NULL check
added MIN/MAX check (as per Mark Byers deleted answer) to check uniqueness