I'm new to SQLite and I am having trouble finding the solution.
I have TABLE1 with columns col1 and col2
col1 col2
-------------
a no
a no
a yes
b no
c yes
c no
d yes
I want no repetitions from col1 but prioritize col2 when having "yes"
I want something like this
col1 col2
-------------
a yes
b no
c yes
d yes
You may try the following:
Approach 1
You may use row_number to retrieve a row number ordered by col2 in descending order that may be used to filter your results eg.
SELECT
col1,
col2
FROM (
SELECT
*,
ROW_NUMBER() OVER (
PARTITION BY col1
ORDER BY col2 DESC
) rn
FROM
my_table
) t
WHERE rn=1;
col1
col2
a
yes
b
no
c
yes
d
yes
Approach 2
or simply use a group by col1 with the MAX function. The group by will ensure that for each col1 value you will receive the MAX of col2 that is yes if available and no if not.
SELECT
col1,
MAX(col2) as col2
FROM
my_table
GROUP BY
col1;
col1
col2
a
yes
b
no
c
yes
d
yes
View working demo on DB Fiddle
ggordon's answer will work well enough, but just since a window function isn't strictly necessary I figured I'd pass another solution:
select distinct
a.col1,
ifnull(b.col2, 'no') col2
from my_table a
left join (
select distinct
col1,
col2
from my_table
where col2 = 'yes'
) b on a.col1 = b.col1
Output:
| col1 | col2 |
| ---- | ---- |
| a | yes |
| b | no |
| c | yes |
| d | yes |
You will first want to do a distinct select on column one. Then you will want to make a case statement which is essentially a if statement in other languages. The case needs to be if column 1 is yes return it. if it is not yes then return no. It would look something like this
CASE
WHEN condition1 THEN result1
WHEN condition2 THEN result2
WHEN conditionN THEN resultN
ELSE result
END;
Related
I have a table A with the following type for data
col1 | col2
--------
e1 | A
e2 | A
e3 | B
e4 | B
.
.
Basically in the col1, the id points to 2 same values. I would like to get a table without the col2 duplication. So something like:
col1 | col2
--------
e1| A
e3| B
e5| C
.
.
Is there a way to achieve this in postgresql? I tried using the distinct keyword but they share the same id ...
You can use group by and min as follows:
Select min(col1) as col1,
Col2
From t
Group by col2;
You can use distinct on:
select distinct on (col2) t.*
from t
order by col2, col1 asc;
This selects all columns on the row.
If you want to delete rows, then you can use:
delete from t
where t.col1 < (select max(t2.col1) from t t2 where t2.col2 = t.col1);
For reasons of our IT department, I am stuck doing this entirely within an SQL query.
Simplified, I have this as an input table:
And I need to create this:
And I am just not sure where to start with this. In my normal C# way of thinking its easy. Column1 is ordered, if the value in Col1 is new, then add a new row to the output and put the contents in column1 in the output. Then, whilst the contents of the input Column1 is unchanged, keep adding the contents of column2 to new rows.
In SQL... nope, I just cannot see the right way to start!
This is a presentation issue that can be easily done in the application or presentation layer. In SQL this can be clunky. The goal of a database is not to render a UI but to store and retrieve data fast and also efficiently, in order to serve as many clients as possible with the same hardware and software resources constraints.
The query that could do this can look like:
with
y as (
select col1, row_number() over(order by col1) as r1
from (select distinct col1 as col1 from t) x
),
z as (
select
t.col1, y.r1, t.col2,
row_number() over(partition by t.col1 order by t.col2) as r2
from t
join y on y.col1 = x.col1
)
select col1, col2
from (
select col1, null as col2, r1, 0 from y
union all
select null, col2, r1, r2 from z
) w
order by r1, r2
As you see, it looks clunky and bloated.
You need a header row for each group which will consist of col1 and null and all the rows of the table with null as col1.
You can do it with UNION ALL and conditional sorting:
select
case when t.col2 is null then t.col1 end col1,
t.col2
from (
select col1, col2 from tablename
union all
select distinct col1, null from tablename
) t
order by
t.col1,
case when t.col2 is null then 1 else 2 end,
t.col2
See the demo (for MySql but it is standard SQL).
Results:
| col1 | col2 |
| ---- | ----- |
| SetA | |
| | BH101 |
| | BH102 |
| | BH103 |
| SetB | |
| | BH201 |
| | BH202 |
| | BH203 |
I agree, formatting should be done outside of SQL, but if you have no choice, here is some SQL Server code that will generate your output
select *
from (
select top 100
case
when col2 is null then ' '+col1
else '' end as firstCol,
IsNull(col2,'') as Col2
from dbo.test t1
group by col1,col2 with rollup
order by col1,col2
) x
where x.firstcol is not null
I have a PSQL table
+--------+------+------+------+
| Col1 | Col2 | Col3 | Col4 |
+--------+------+------+------+
| 001 | 00A | 00B | 001 |
| 001001 | 00A | 00B | 001 |
| 002 | 00X | 00Y | 002 |
| 002002 | 00X | 00Y | 002 |
+--------+------+------+------+
I have the following PSQL query:
select *
from my_table
where (Col1 = '001' or Col4 = '001')
and Col2 = '00A'
order by Col3 asc;
I get the first two rows.
Here what happens is that it matches both conditions for OR condition. I need to match only one of the or conditions. That is if first condition (Col1='001001') is true then do not evaluate the next condition.
I need to select only the 2nd row (| 001001 | 00A | 00B | 001 |)
I have build another query using EXCEPT
select *
from my_table
where (Col1 = '001' or Col4 = '001')
and Col2 = '00A'
except (select *
from my_table
where Col1 != '001'
and Col2 = '00A')
order by Col3 asc
limit 1;
I would like to know if there is any other elegant queries for this job?
Your explanation is confusing as you say col1 = '001001' in one place and use 001 in the query. But I presume you want to use a hierarchy of comparison and return the one with the highest per each group ( col2,col3,col4) . Use DISTINCT ON. Change the condition in whichever way you like to return the appropriate row.
SELECT DISTINCT ON (col2, col3, col4) *
FROM my_table WHERE col2 = '00A'
ORDER BY col2,
col3,
col4,
CASE
WHEN col1 = '001001' THEN 1
WHEN col4 = '001' THEN 2
END;
DEMO
Does this give you what you want?
select *
from my_table
where (Col1 = '001' and Col2 != '00A')
or ((Col1 is null or Col1 = '') and Col4 = '001' and Col2 = '00A')
order by Col3 asc;
I have a table tab1 that looks like this:
col1 | col2 | col3
------|------|------
abc | 100 | text
abc | 100 | text
abc | 100 | text
... | ... | ...
I need to update col2 value in each row like this:
update tab1
set col2 = 1,23
when mod(rownum,10) = 1;
update tab1
set col2 = 12,34
when mod(rownum,10) = 2;
update tab1
set col2 = 123,45
when mod(rownum,10) = 3;
and etc. until when mod(rownum,10) = 9.
But obviously this query doesn't work, and the reason is that rownum always returns 1 in this situation, afaik. However, I've got the correct last digits for each row number with select mod(rownum,10) as lastDig from tab1 query. But I don't understand how to use the result of this select for my update when conditions.
Could you please provide an example of a query that will do the job in this situation? Do I need to use a subquery or select in a temporary table? Please explain. I'm a junior frontend guy, but I need to create a demo table this way. I believe, pl/sql is v10, as well as PL/SQL Developer.
Result wanted looks like this:
col1 | col2 | col3
------|-------|------
abc | 1.23 | text
abc | 12.34 | text
abc | 123.45| text
... | ... | ...
You could use CASE expression or DECODE:
update tab1
set col2 = CASE mod(rownum,10) WHEN 1 THEN 1.23
WHEN 2 THEN 12.34
WHEN 3 THEN 123.45
-- ...
ELSE col2
END
-- WHERE ...
UPDATE tab1
SET col2 = DECODE(mod(rownum,10), 1, 1.23, 2, 12.34, 3, 123.45, ..., col2)
-- WHERE ...;
DBFiddle Demo
You have not told us if there is a specific order in which you want to treat rows as 1,2,3 .. If there is indeed an order, then ROWNUM is unreliable and may not work, you would need row_number() with a specific order by column. That can be combined with a MERGE statement.
MERGE INTO tab1 tgt USING (
SELECT
CASE mod( ROW_NUMBER() OVER(
ORDER BY
col1 -- the column which is in order and unique
),10)
WHEN 1 THEN 1.23
WHEN 2 THEN 12.34
WHEN 3 THEN 123.45
--..
--.. 9
ELSE col2
AS col2
FROM
tab1 t
)
src ON ( tgt.rowid = src.rowid ) --use primary key/unique key if there is one instead of rowid
WHEN MATCHED THEN UPDATE SET tgt.col2 = src.col2;
Demo
Say I have this table
| Col |
-------
| ABC |
| DEF |
What query should I write to obtain this result (not literally this result, but a general way to do that)?
| Col | Col2 |
--------------
| ABC | 0 |
| ABC | 1 |
| DEF | 0 |
| DEF | 1 |
Unless I'm missing something, this should give you the results you're looking for:
Select Col, Col2
From YourTable
Cross Join (Select 0 As Col2 Union Select 1 As Col2) X
Order By Col, Col2
I would guess that you want to pair two columns, for each combination. Your question is vague and not specific to a problem. That's my assumption.
I guess this query could do:
Select Table1.Col1, Table2.Col2 from Table1 LEFT JOIN Table2 on 1=1
This way, you pair up every row from table1 with every row from table2.
Edit, without table2:
Select Table1.Col1, Constructed.Col1 from Table1 LEFT JOIN
(Select 1 as Col1 UNION Select 2 as Col1 UNION
Select 7 as Col1 UNION Select 14 as Col1) Constructed on 1=1
Can you test query, is this what you want?
select * from
(select col1, 0 b from table) table1
union all (select col1, 1 b from table) order by 1;