I need to update a table based on a value derived from case logic. That case logic is created using several other tables, such as this:
CASE
WHEN column = 'value'
THEN
COALESCE
(
CASE WHEN column = 'test1' THEN 'result' END,
CASE WHEN column = 'test2' THEN 'result' END
)
ELSE
column
END AS Derived_Column
FROM
table_a a
LEFT JOIN table_b b ON a.column = b.column
LEFT JOIN tabel_c c ON b.column = c.column
What I need to to do something like this:
UPDATE table SET column =
( SELECT column FROM table WHERE column = <CASE STATEMENT LOGIC>)
Somehow I need to updated the column in the table filtering on the the output of Derived_Column. So I need to check against a sub query or something of that nature.
Would anyone know how to do this?
Related
I have two columns in the same table that I want to join in Postgresql but for some reason I’m getting this error. Don’t know how to figure it out. Please help.
[42P01] ERROR: relation "a" does not exist
Position: 10
X table contains two pools(ABC,XYZ), ids, numbers and description. If an ID exists in one pool but not in the other, it should update description column to “ADD”. Pools need to be joined on number.
UPDATE A
SET A.Description = 'ADD'
FROM X AS A
LEFT JOIN X AS B ON B.number = A.number
AND B.id = 'ABC'
WHERE A.id = 'XYZ'
AND B.number IS NULL
AND A.Description IS NULL;
With standard SQL you can't do a join as part of an update, but what you can do is include a subquery to select the id's to update. The subquery can contain a join. I'm not entirely clear on what you're actually trying to accomplish, but you could do something like this:
UPDATE x SET description='ADD' WHERE number IN (
SELECT a.number FROM x AS a
LEFT OUTER JOIN x AS b ON a.number=b.number AND a.id='XYZ' AND b.id='ABC'
WHERE b.number IS NULL
);
This will join the table x with itself and will select (and update) any numbers's that don't have a matching number in the 'ABC' and 'XYZ' zone.
PostgreSQL does have a UPDATE FROM syntax that does let you update with complex subqueries. It's more flexible but it's non-standard. You can find an example of this type of query here.
I'm trying to decipher another programmer's code who is long-gone, and I came across a select statement in a stored procedure that looks like this (simplified) example:
SELECT #Table2.Col1, Table2.Col2, Table2.Col3, MysteryColumn = CASE WHEN y.Col3 IS NOT NULL THEN #Table2.MysteryColumn - y.Col3 ELSE #Table2.MysteryColumn END
INTO #Table1
FROM #Table2
LEFT OUTER JOIN (
SELECT Table3.Col1, Table3.Col2, Col3 = SUM(#Table3.Col3)
FROM Table3
INNER JOIN #Table4 ON Table4.Col1 = Table3.Col1 AND Table4.Col2 = Table3.Col2
GROUP BY Table3.Col1, Table3.Col2
) AS y ON #Table2.Col1 = y.Col1 AND #Table2.Col2 = y.Col2
WHERE #Table2.Col2 < #EnteredValue
My question, what does the fourth column of the primary selection do? does it produce a boolean value checking to see if the values are equal? or does it set the #Table2.MysteryColumn equal to some value and then inserts it into #Table1? Or does it just update the #Table2.MysteryColumn and not output a value into #Table1?
This same thing seems to happen inside of the sub-query on the third column, and I am equally at a loss as to what that does as well.
MysteryColumn = gives the expression a name also called a column alias. The fact that a column in the table#2 also has the same name is besides the point.
Since it uses INTO syntax it also gives the column its name in the resulting temporary table. See the SELECT CLAUSE and note | column_alias = expression and the INTO CLAUSE
I have tried this:
SELECT *
FROM svc00100
WHERE NOT EXISTS (SELECT *
FROM svc00101
WHERE TECHSTAT = 'INA'
AND svc00100.TECHID = svc00101.TECHID)
I want to select rows from svc00100 but not if there is a row in svc00101 with the same TECHID and with TECHSTAT = 'INA'. But, there are multiple rows in svc00101 with the TECHID matching, some having 'INA' and some having other stuff. I want to eliminate/ignore any TECHID where there is any row in svc00101 with TECHID and 'INA' for techstat. Using SQL server BTW if that helps.
You can use left outer join and Where clause. Like this:
select svc00100.* from svc00100
left outer join svc00101 on TECHSTAT = "INA"
and svc00100.TECHID = svc00101.TECHID
where svc00101.KEY is null
Instead of KEY you should pass name of NOT NULL column. For example Primary Key.
Is there any other way for returning rows for the same id by joining two tables and return the row if any of the columns value for the same id is different.
Select Table1.No,Table2.No,Table1.Name,Table2.Name,Table1.ID,Table2.ID,Table1.ID_N,Table2.ID_N
From MyFirstTable Table1
JOIN MySecondTable Table2
ON Table1.No=Table2.No where Table1.ID!=Table2.ID or Table1.ID_N != Table2.ID_N
In the example above , I have only two columns I need to check but in my real case there are at least 20 .
Is there any other statment I can use instead of enumerating each column in the where codition?
...WHERE BINARY_CHECKSUM(Table1.*) <> BINARY_CHECKSUM(Table2.*)
or
...WHERE BINARY_CHECKSUM(Table1.Field1, Table1.Field2, ...) <> BINARY_CHECKSUM(Table2..Field1, Table2.Field2, ...)
*this assumes you have no blob fields in your tables
http://technet.microsoft.com/en-us/library/ms173784.aspx
If No is a PK
Select Table1.No,Table1.Name,Table1.ID,Table1.ID_N
From MyFirstTable Table1
except
Select Table1.No,Table1.Name,Table1.ID,Table1.ID_N
From MySecondTable Table1
I have a lengthy query here, and wondering whether it could be refactor?
Declare #A1 as int
Declare #A2 as int
...
Declare #A50 as int
SET #A1 =(Select id from table where code='ABC1')
SET #A2 =(Select id from table where code='ABC2')
...
SET #A50 =(Select id from table where code='ABC50')
Insert into tableB
Select
Case when #A1='somevalue' Then 'x' else 'y' End,
Case when #A2='somevalue' Then 'x' else 'y' End,
..
Case when #A50='somevalue' Then 'x' else 'y' End
From tableC inner join ......
So as you can see from above, there is quite some redundant code. But I can not think of a way to make it simpler.
Any help is appreciated.
If you need the variables assigned, you could pivot your table...
SELECT *
FROM
(
SELECT Code, Id
FROM Table
) t
PIVOT
(MAX(Id) FOR Code IN ([ABC1],[ABC2],[ABC3],[ABC50])) p /* List them all here */
;
...and then assign them accordingly.
SELECT #A1 = [ABC1], #A2 = [ABC2]
FROM
(
SELECT Code, Id
FROM Table
) t
PIVOT
(MAX(Id) FOR Code IN ([ABC1],[ABC2],[ABC3],[ABC50])) p /* List them all here */
;
But I doubt you actually need to assign them at all. I just can't really picture what you're trying to achieve.
Pivotting may help you, as you can still use the CASE statements.
Rob
Without taking the time to develop a full answer, I would start by trying:
select id from table where code in ('ABC1', ... ,'ABC50')
then pivot that, to get one row result set of columns ABC1 through ABC50 with ID values.
Join that row in the FROM.
If 'somevalue', 'x' and 'y' are constant for all fifty expressions. Then start from:
select case id when 'somevalue' then 'x' else 'y' end as XY
from table
where code in ('ABC1', ... ,'ABC50')
I am not entirely sure from your example, but it looks like you should be able to do one of a few things.
Create a nice look up table that will tell you for a given value of the select statement what should be placed there. This would be much shorter and should be insanely fast.
Create a simple for loop in your code and generate a list of 50 small queries.
Use sub-selects or generate a list of selects with one round trip to retrieve your #a1-#A50 values and then generate the query with them already in place.
Jacob