Using select and case statement in SQL
How to make the 4th column "1" if next row of LETTER column is D. See example below:
https://i.stack.imgur.com/br4dn.png
You can combine CASE with LEAD(). Assuming you are ordering by stepthe query can look like:
select
t.*,m
case when lead(letter) over(order by step) = 'D'
then 1 else 0 end as is_next_row_letter_d
from t
Assuming that the STEP column provides the ordering and that it is continuous, we could use a self-join approach here:
SELECT t1.STEP, t1.ID, t1.LETTER,
CASE WHEN t2.LETTER = 'D' THEN 1 ELSE 0 END AS IS_NEXT_D
FROM yourTable t1
LEFT JOIN yourTable t2
ON t2.STEP = t1.STEP + 1
ORDER BY t1.STEP;
Related
I've already found so many answers here but now I can't seem to find any to my specific problem.
I can't figure out how to select a value from a row depending on the value in different columns
with the below table, I want to achieve the following results.
in case the value in column stdvpuni = 1 then return values / contents from this row for the article (column art).
in case the value in column stdvpuni = 0 then return values / contents from the row where STDUNIABG = 1 for this article (column art).
You seem to want one row part art, based on the content of other rows. That suggests using row_number():
select t.*
from (select t.*,
row_number() over (partition by art order by stdvpuni desc, STDUNIABG desc) as seqnum
from t
) t
where seqnum = 1;
You don't specify what to do if neither column is 1. You might want a where clause (where 1 in (stdvpuni, STDUNIABG)) or another condition in the order by.
I do not know what values / contents is, but I suppose that's easy for you to figure out. So, I will focus on the way to select this:
SELECT
CASE
WHEN current.stdvpuni = 1 THEN 'values / contents of current row'
ELSE 'values / contents of other row'
END
FROM yourtable current
JOIN yourtable other
ON other.stdvpuni = 1;
Use your conditions with NOT EXISTS in the WHERE clause:
SELECT t1.*
FROM tablename t1
WHERE t1.STDVPUNI = 1
OR (
t1.STDVPUNI = 0 AND t1.STDUNIABG = 1
AND NOT EXISTS (SELECT 1 FROM tablename t2 WHERE t2.ART = t1.ART AND t2.STDVPUNI = 1)
);
I have a table with returns such as 12X90, 12X120, 12X160, etc.
The numbers after the "X" are weights. I need to pad the weights only with leading zeros so that 90 become 090. A normal sort will put the 90 last instead of first, I need the list sorted correctly, by weight.
How can I achieve that?
Use charindex to get the number after X in the column and order by that number.
select * from tablename
order by cast(case when charindex('X',col) > 0 then substring(col,charindex('X',col)+1,len(col))
else col end as numeric)
If the string before X should also be considered for sorting, use
select * from tablename
order by
cast(case when charindex('X',col) > 0 then substring(col,1,charindex('X',col)-1)
else col end as numeric)
,cast(case when charindex('X',col) > 0 then substring(col,charindex('X',col)+1,len(col))
else col end as numeric)
Sample demo
use a cross apply
select
b.* from table t1
cross apply
(select replace(t.weight,'12x','') as replaced from table t2 where t2.weight=t1.weight) b
order by b.replaced
I have a table of items by date (each row is a new date). I am drawing out a value from another column D. I need it to replace 0s though. I need the following logic: when D=0 for that date, use the value in column D from the date prior.
Actually, truth be told, I need it to say, when D is 0, use the value from the latest date where D was not a 0, but the first will get me most of the way there.
Is there a way to build this logic? Maybe a CTE?
Thank you very much.
PS I'm using SSMS 2008.
EDIT: I wasn't very clear at first. The value I want to change is not the date. I want change the value in D with the latest non-zero value from D, based on date.
May be the following query might help you. It uses the OUTER APPLY to fetch the results. Screenshot #1 shows the sample data and query output against the sample data. This query can be written better but this is what I could come up with right now.
Hope that helps.
SELECT ITM.Id
, COALESCE(DAT.New_D, ITM.D) AS D
, ITM.DateValue
FROM dbo.Items ITM
OUTER APPLY (
SELECT
TOP 1 D AS New_D
FROM dbo.Items DAT
WHERE DAT.DateValue < ITM.DateValue
AND DAT.D <> 0
AND ITM.D = 0
ORDER BY DAT.DateValue DESC
) DAT
Screenshot #1:
UPDATE t
Set value = SELECT value
FROM table
WHERE date = (SELECT MAX(t1.date)
FROM table t1
WHERE t1.value != 0
AND t1.date < t.date)
FROM table t
WHERE t.value = 0
You could maybe something like this as part of an update script...
SET myTable.D = (
SELECT TOP 1 myTable2.D
FROM myTable2
WHERE myTable2.myDateField < myTable.myDateField
AND myTable2.D != 0
ORDER BY myTable2.myDateField DESC)
That's assuming that you want to actually update the data though rather than just replace the values for the purpose of a select query.
How about:
SELECT
i.ID,
i.DateValue,
D = CASE WHEN I.D <> 0 THEN I.D ELSE X.D END
FROM
Items I
OUTER APPLY (
SELECT TOP 1 S.D
FROM Items S
WHERE S.DATEVALUE < I.DATEVALUE AND S.D <> 0
ORDER BY S.DATEVALUE DESC
) X
SELECT t.id,
CASE WHEN t.D = 0 THEN t0.D
ELSE t.D END
FROM table AS t
LEFT JOIN table AS t0
ON t0.time =
(
SELECT MAX(time) FROM t0
WHERE t0.time < t.time
AND t0.D != 0
)
or if you want to avoid aggregates entirely,
SELECT t.id,
CASE WHEN t.D = 0 THEN t0.D
ELSE t.D END
FROM table AS t
LEFT JOIN table AS t0
ON t0.time < t.time
LEFT JOIN table AS tx
ON tx.time > t0.time
WHERE t0.D != 0
AND tx.D != 0
AND tx.id IS NULL -- i.e. there isn't any
Is it possible to alias a column name and then use that in a CASE statement? For example,
SELECT col1 as a, CASE WHEN a = 'test' THEN 'yes' END as value FROM table;
I am trying to alias the column because actually my CASE statement would be generated programmatically, and I want the column that the case statement uses to be specified in the SQL instead of having to pass another parameter to the program.
This:
SELECT col1 as a,
CASE WHEN a = 'test' THEN 'yes' END as value
FROM table;
...will not work. This will:
SELECT CASE WHEN a = 'test' THEN 'yes' END as value
FROM (SELECT col1 AS a
FROM TABLE)
Why you wouldn't use:
SELECT t.col1 as a,
CASE WHEN t.col1 = 'test' THEN 'yes' END as value
FROM TABLE t;
...I don't know.
I think that MySql and MsSql won't allow this because they will try to find all columns in the CASE clause as columns of the tables in the WHERE clause.
I don't know what DBMS you are talking about, but I guess you could do something like this in any DBMS:
SELECT *, CASE WHEN a = 'test' THEN 'yes' END as value FROM (
SELECT col1 as a FROM table
) q
#OMG Ponies - One of my reasons of not using the following code
SELECT t.col1 as a,
CASE WHEN t.col1 = 'test' THEN 'yes' END as value
FROM TABLE t;
can be that the t.col1 is not an actual column in the table. For example, it can be a value from a XML column like
Select XMLColumnName.value('(XMLPathOfTag)[1]', 'varchar(max)')
as XMLTagAlias from Table
It should work. Try this
Select * from
(select col1, col2, case when 1=1 then 'ok' end as alias_col
from table)
as tmp_table
order by
case when #sortBy = 1 then tmp_table.alias_col end asc
I use CTEs to help compose complicated SQL queries but not all RDBMS' support them. You can think of them as query scope views. Here is an example in t-sql on SQL server.
With localView1 as (
select c1,
c2,
c3,
c4,
((c2-c4)*(3))+c1 as "complex"
from realTable1)
, localView2 as (
select case complex WHEN 0 THEN 'Empty' ELSE 'Not Empty' end as formula1,
complex * complex as formula2
from localView1)
select *
from localView2
Nor in MsSql
SELECT col1 AS o, e = CASE WHEN o < GETDATE() THEN o ELSE GETDATE() END
FROM Table1
Returns:
Msg 207, Level 16, State 3, Line 1
Invalid column name 'o'.
Msg 207, Level 16, State 3, Line 1
Invalid column name 'o'.
However if I change to CASE WHEN col1... THEN col1 it works
If you write only equal condition just:
Select Case columns1 When 0 then 'Value1'
when 1 then 'Value2' else 'Unknown' End
If you want to write greater , Less then or equal you must do like this:
Select Case When [ColumnsName] >0 then 'value1' When [ColumnsName]=0 Or [ColumnsName]<0 then
'value2'
Else
'Unkownvalue' End
From tablename
Thanks
Mr.Buntha Khin
SELECT
a AS [blabla a],
b [blabla b],
CASE c
WHEN 1 THEN 'aaa'
WHEN 2 THEN 'bbb'
ELSE 'unknown'
END AS [my alias],
d AS [blabla d]
FROM mytable
Not in MySQL. I tried it and I get the following error:
ERROR 1054 (42S22): Unknown column 'a' in 'field list'
In MySql, alice name may not work, therefore put the original column name in the CASE statement
SELECT col1 as a, CASE WHEN col1 = 'test' THEN 'yes' END as value FROM table;
Sometimes above query also may return error, I don`t know why (I faced this problem in my two different development machine). Therefore put the CASE statement into the "(...)" as below:
SELECT col1 as a, (CASE WHEN col1 = 'test' THEN 'yes' END) as value FROM table;
Yes, you just need to add a parenthesis :
SELECT col1 as a, (CASE WHEN a = 'test' THEN 'yes' END) as value FROM table;
make it so easy.
select columnnameshow = (CASE tipoventa
when 'CONTADO' then 'contadito'
when 'CREDITO' then 'cred'
else 'no result'
end) from Promocion.Promocion
We've got some SQL code I'm trying to optimize. In the code is a view that is rather expensive to run. For the sake of this question, let's call it ExpensiveView. On top of the view there is a query that joins the view to itself via a two sub-queries.
For example:
select v1.varCharCol1, v1.intCol, v2.intCol from (
select someId, varCharCol1, intCol from ExpensiveView where rank=1
) as v1 inner join (
select someId, intCol from ExpensiveView where rank=2
) as v2 on v1.someId = v2.someId
An example result set:
some random string, 5, 10
other random string, 15, 15
This works, but it's slow since I'm having to select from ExpensiveView twice. What I'd like to do is use a case statement to only select from ExpensiveView once.
For example:
select someId,
case when rank = 1 then intCol else 0 end as rank1IntCol,
case when rank = 2 then intCol else 0 end as rank2IntCol
from ExpensiveView where rank in (1,2)
I could then group the above results by someId and get almost the same thing as the first query:
select sum(rank1IntCol), sum(rank2Intcol)
from ( *the above query* ) SubQueryData
group by someId
The problem is the varCharCol1 that I need to get when the rank is 1. I can't use it in the group since that column will contain different values when rank is 1 than it does when rank is 2.
Does anyone have any solutions to optimize the query so it only selects from ExpensiveView once and still is able to get the varchar data?
Thanks in advance.
It's hard to guess since we don't see your view definition, but try this:
SELECT MIN(CASE rank WHEN 1 THEN v1.varCharCol1 ELSE NULL END),
SUM(CASE rank WHEN 1 THEN rank1IntCol ELSE 0 END),
SUM(CASE rank WHEN 2 THEN rank2IntCol ELSE 0 END)
FROM query
GROUP BY
someId
Note that in most cases for the queries like this:
SELECT *
FROM mytable1 m1
JOIN mytable1 m2
ON …
the SQL Server optimizer will just build an Eager Spool (a temporary index), which will later be used for searching for the JOIN condition, so probably these tricks are redundant.
select someId,
case when rank = 1 then varCharCol1 else '_' as varCharCol1
case when rank = 1 then intCol else 0 end as rank1IntCol,
case when rank = 2 then intCol else 0 end as rank2IntCol
from ExpensiveView where rank in (1,2)
then use min() or max in the enclosing query