Suppose I have 10 columns in my table and I want to update each column but one at a time for each row up to 10 rows.
if table is like
1,2,3
4,5,6
7,8,9
I want to update it like
x,2,3
4,y,6
7,8,z
Columns can be of any count so need dynamic approach. Also sometimes need to exclude some columns.
I tried to see if I can update row based on row id but there is no such option available as row id. I don't wanna change design of table to include a counter column.
you can use window function to assign a a row id and based on that :
with cte as (
select * from (
select * , row_number() over (order by id) rn
from tablename
) t ) ;
update t
set col1 = case when rn = 1 then <updatevalue> else col1 end
, col2 = case when rn = 2 then <updatevalue> else col2 end
, col3 = case when rn = 3 then <updatevalue> else col3 end
, ...
from tablename t
join cte on cte.id = t.id
The requirement "Columns can be of any count so need dynamic approach" looks like as a try to implement matrix as a table.
Alternative approach could be usage of ARRAY type and storing entire structure as single "cell" in the table.
CREATE OR REPLACE TABLE t
AS
SELECT ARRAY_CONSTRUCT(ARRAY_CONSTRUCT(1,2,3),
ARRAY_CONSTRUCT(4,5,6),
ARRAY_CONSTRUCT(7,8,9)) c
UNION ALL
SELECT ARRAY_CONSTRUCT(ARRAY_CONSTRUCT(10,20,30),
ARRAY_CONSTRUCT(40,50,60),
ARRAY_CONSTRUCT(70,80,90)) c;
SELECT *
FROM t;
/*
C
[[1,2,3],[4,5,6],[7,8,9]]
[[10,20,30],[40,50,60],[70,80,90]]
*/
Accessing elements:
SELECT c[0][0], c[0][1], c[0][2],
c[1][0], c[1][1], c[1][2],
c[2][0], c[2][1], c[2][2]
FROM t;
/*
C[0][0] C[0][1] C[0][2] C[1][0] C[1][1] C[1][2] C[2][0] C[2][1] C[2][2]
1 2 3 4 5 6 7 8 9
10 20 30 40 50 60 70 80 90
*/
Update:
UPDATE t
SET c = ARRAY_CONSTRUCT(ARRAY_CONSTRUCT('x' , c[0][1], c[0][2])
,ARRAY_CONSTRUCT(c[1][0], 'y' ,c[1][2])
,ARRAY_CONSTRUCT(c[2][0], c[2][1] , 'z' )
);
SELECT * FROM t;
/*
C
[["x",2,3],[4,"y",6],[7,8,"z"]]
[["x",20,30],[40,"y",60],[70,80,"z"]]
*/
More robust transformations could be performed via user-defined functions.
Related
I am searching with a query
--Code Format
SELECT COLA,COLB,COLC from MYTABLE where SWITCH IN (1,2,3);
If MYTABLE does not contain rows with SWITCH 1,2 or 3 I need default values returned along with the SWITCH value. How do I do it?
Below is my table format
COLA | COLB | COLC | SWITCH
------------------------------
A B C 1
a b c 2
i want a query when I search with
select * from MYTABLE where switch in (1,2,3)
That gets results like this --
COLA | COLB | COLC | SWITCH
------------------------------
A B C 1
a b c 2
NA NA NA 3
--Check to see if any row exists matching your conditions
IF NOT EXISTS (SELECT COLA,COLB,COLC from MYTABLE where SWITCH IN (1,2,3))
BEGIN
--Select your default values
END
ELSE
BEGIN
--Found rows, return them
SELECT COLA,COLB,COLC from MYTABLE where SWITCH IN (1,2,3)
END
if not exists( SELECT 1 from MYTABLE where SWITCH IN (1,2,3))
select default_value
How about:
SELECT COLA,COLB,COLC from MYTABLE where SWITCH IN (1,2,3)
union select 5555, 6666, 7777 where not exists (
SELECT COLA,COLB,COLC from MYTABLE where SWITCH IN (1,2,3)
);
5555, 6666, 7777 being the default row in case there aren't any rows matching your criteria.
Here is one way to tackle this. You need a table of the SWITCH values you want to look at. Then a simple left join makes this super easy.
select ColA
, ColB
, ColC
v.Switch
from
(
values
(1)
, (2)
, (3)
)v (Switch)
left join YourTable yt on yt.Switch = v.Switch
You can Use a Split Function And Left Join As Shown Below:
Select ISNULL(ColA,'NA') As ColA,ISNULL(ColB,'NA') As ColB,ISNULL(ColC,'NA') As ColC,ISNULL(Switch,a.splitdata)
from [dbo].[fnSplitString]('1,2,3',',') a
LEFT JOIN #MYTABLE t on a.splitdata=t.Switch
[dbo].[fnSplitString] is a Split Function with 2 arguments - Delimeter Separated String and Delimeter and Output a Table.
EDIT:
Given the new explanation, I changed the answer completely. I think I got your question now:
SELECT * FROM MYTABLE AS mt
RIGHT JOIN (SELECT 1 AS s UNION SELECT 2 AS s UNION SELECT 3 AS s) AS st
ON st.s = mt.SWITCH
You could change the SELECT 1 AS s UNION SELECT 2 AS s UNION SELECT 3 AS spart to a subquery that results in all possible values SWITCH could assume. E.g.:
SELECT DISTINCT SWITCH FROM another_table_with_all_switches
If all want is the value of switch that is not in MYTABLE, not the whole table with null values, you could try:
SELECT * FROM
(SELECT 1 AS s UNION SELECT 2 AS s UNION SELECT 3) AS st
WHERE st.s NOT IN (SELECT DISTINCT SWITCH FROM MYTABLE)
I want the server to give me the results of a query in the order I send it.
So if I write:
SELECT * FROM table WHERE column in (9,1,8)
I would like it to give me the results in the order: 9,1,8
One method uses left join:
select t.*
from (select 9 as c, 1 as priority union all select 1, 2 union all select 8, 3
) vals left join
table t
on t.column = vals.c
order by vals.priority;
Note: This is generic syntax. The specific syntax for the subquery may differ depending on the database.
Another method uses case in the order by:
select t.*
from table t
where t.column in (9, 1, 8)
order by (case column when 9 then 1 when 1 then 2 when 8 then 3 end);
Once again, this can be simplified in some databases, say by using special functions.
You could use CASE expression in order you want, something like:
select *
from table_name
where column_name in (9,1,8)
order by case column_name
when 9 then 1
when 1 then 2
when 8 then 3 end
, column_name -- optional, but here could go another column if you want to have custom order
You can do in Oracle SQL if you have
SELECT Column_name
FROM user_tab_columns
where table_name = 'MY_TABLE'
and Column_id in (9,1,8)
SELECT *
FROM table
WHERE column IN (9, 1, 8)
ORDER BY CASE WHEN column = 9 THEN 1
WHEN column = 1 THEN 2
WHEN column = 8 THEN 3
END
I have a table and I want to group rows that have at most x difference at col2.
For example,
col1 col2
abg 3
abw 4
abc 5
abd 6
abe 20
abf 21
After query I want to get groups such that
group 1: abg 3
abw 4
abc 5
abd 6
group 2: abe 20
abf 21
In this example difference is 1.
How can write such a query?
For Oracle (or anything that supports window functions) this will work:
select col1, col2, sum(group_gen) over (order by col2) as grp
from (
select col1, col2,
case when col2 - lag(col2) over (order by col2) > 1 then 1 else 0 end as group_gen
from some_table
)
Check it on SQLFiddle.
This should get what you need, and changing the gap to that of 5, or any other number is a single change at the #lastVal +1 (vs whatever other difference). The prequery "PreSorted" is required to make sure the data is being processed sequentially so you don't get out-of-order entries.
As each current row is processed, it's column 2 value is stored in the #lastVal for test comparison of the next row, but remains as a valid column "Col2". There is no "group by" as you are just wanting a column to identify where each group is associated vs any aggregation.
select
#grp := if( PreSorted.col2 > #lastVal +1, #grp +1, #grp ) as GapGroup,
PreSorted.col1,
#lastVal := PreSorted.col2 as Col2
from
( select
YT.col1,
YT.col2
from
YourTable YT
order by
YT.col2 ) PreSorted,
( select #grp := 1,
#lastVal := -1 ) sqlvars
try this query, you can use 1 and 2 as input and get you groups:
var grp number(5)
exec :grp :=1
select * from YourTABLE
where (:grp = 1 and col2 < 20) or (:grp = 2 and col2 > 6);
I would like to use the IN clause, but with the convert function.
Basically, I have a table (A) with the column of type int.
But in the other table (B) I Have values which are of type varchar.
Essentially, what I am looking for something like this
select *
from B
where myB_Column IN (select myA_Columng from A)
However, I am not sure if the int from table A, would map / convert / evaluate properly for the varchar in B.
I am using SQL Server 2008.
You can use CASE statement in where clause like this and CAST only if its Integer.
else 0 or NULL depending on your requirements.
SELECT *
FROM B
WHERE CASE ISNUMERIC(myB_Column) WHEN 1 THEN CAST(myB_Column AS INT) ELSE 0 END
IN (SELECT myA_Columng FROM A)
ISNUMERIC will be 1 (true) for Decimal values as-well so ideally you should implement your own IsInteger UDF .To do that look at this question
T-sql - determine if value is integer
Option #1
Select * from B where myB_Column IN
(
Select Cast(myA_Columng As Int) from A Where ISNUMERIC(myA_Columng) = 1
)
Option #2
Select B.* from B
Inner Join
(
Select Cast(myA_Columng As Int) As myA_Columng from A
Where ISNUMERIC(myA_Columng) = 1
) T
On T.myA_Columng = B.myB_Column
Option #3
Select B.* from B
Left Join
(
Select Cast(myA_Columng As Int) As myA_Columng from A
Where ISNUMERIC(myA_Columng) = 1
) T
On T.myA_Columng = B.myB_Column
I will opt third one. Reason is below mentioned.
Disadvantages of IN Predicate
Suppose I have two list objects.
List 1 List 2
1 12
2 7
3 8
4 98
5 9
6 10
7 6
Using Contains, it will search for each List-1 item in List-2 that means iteration will happen 49 times !!!
You can also use exists caluse,
select *
from B
where EXISTS (select 1 from A WHERE CAST(myA_Column AS VARCHAR) = myB_Column)
You can use below query :
select B.*
from B
inner join (Select distinct MyA_Columng from A) AS X ON B.MyB_Column = CAST(x.MyA_Columng as NVARCHAR(50))
Try it by using CAST()
SELECT *
FROM B
WHERE CAST(myB_Column AS INT(11)) IN (
SELECT myA_Columng
FROM A
)
Let's say I have an sql server table:
NumberTaken CompanyName
2 Fred 3 Fred 4 Fred 6 Fred 7 Fred 8 Fred 11 Fred
I need an efficient way to pass in a parameter [StartingNumber] and to count from [StartingNumber] sequentially until I find a number that is missing.
For example notice that 1, 5, 9 and 10 are missing from the table.
If I supplied the parameter [StartingNumber] = 1, it would check to see if 1 exists, if it does it would check to see if 2 exists and so on and so forth so 1 would be returned here.
If [StartNumber] = 6 the function would return 9.
In c# pseudo code it would basically be:
int ctr = [StartingNumber]
while([SELECT NumberTaken FROM tblNumbers Where NumberTaken = ctr] != null)
ctr++;
return ctr;
The problem with that code is that is seems really inefficient if there are thousands of numbers in the table. Also, I can write it in c# code or in a stored procedure whichever is more efficient.
Thanks for the help
A solution using JOIN:
select min(r1.NumberTaken) + 1
from MyTable r1
left outer join MyTable r2 on r2.NumberTaken = r1.NumberTaken + 1
where r1.NumberTaken >= 1 --your starting number
and r2.NumberTaken is null
I called my table Blank, and used the following:
declare #StartOffset int = 2
; With Missing as (
select #StartOffset as N where not exists(select * from Blank where ID = #StartOffset)
), Sequence as (
select #StartOffset as N from Blank where ID = #StartOffset
union all
select b.ID from Blank b inner join Sequence s on b.ID = s.N + 1
)
select COALESCE((select N from Missing),(select MAX(N)+1 from Sequence))
You basically have two cases - either your starting value is missing (so the Missing CTE will contain one row), or it's present, so you count forwards using a recursive CTE (Sequence), and take the max from that and add 1
Edit from comment. Yes, create another CTE at the top that has your filter criteria, then use that in the rest of the query:
declare #StartOffset int = 2
; With BlankFilters as (
select ID from Blank where hasEntered <> 1
), Missing as (
select #StartOffset as N where not exists(select * from BlankFilters where ID = #StartOffset)
), Sequence as (
select #StartOffset as N from BlankFilters where ID = #StartOffset
union all
select b.ID from BlankFilters b inner join Sequence s on b.ID = s.N + 1
)
select COALESCE((select N from Missing),(select MAX(N)+1 from Sequence))
this may now return a row that does exist in the table, but hasEntered=1
Tables:
create table Blank (
ID int not null,
Name varchar(20) not null
)
insert into Blank(ID,Name)
select 2 ,'Fred' union all
select 3 ,'Fred' union all
select 4 ,'Fred' union all
select 6 ,'Fred' union all
select 7 ,'Fred' union all
select 8 ,'Fred' union all
select 11 ,'Fred'
go
Try the set based approach - should be faster
select min(t1.NumberTaken)+1 as "min_missing" from t t1
where not exists (select 1 from t t2
where t1.NumberTaken = t2.NumberTaken+1)
and t1.NumberTaken > #StartingNumber
This is Sybase syntax, so massage for SQL server consumption if needed.
Create a temp table with all numbers from StartingValue to EndValue and LEFT OUTER JOIN to your data table.