I have a DB with two columns with many records and from these two columns I have to do some mathematical operations and create other two columns.
For now I did like this:
I made a SELECT and read the two columns, and put everything in a List
Then I go through the List and UPDATE the table line by line
Do you think there is a faster way to do it? I also tried like this:
UPDATE myTable SET X_GAUSS = (SELECT X FROM myTable ) + 1, Y_GAUSS = (SELECT Y FROM myTable) + 2
(it's only an example)
But in this way every line of the new columns is the same as the line before, instead I want something like:
X Y X_GAUSS Y_GAUSS
1 2 2 4
3 4 4 6
5 6 6 8
...
A subquery like SELECT X FROM myTable returns the first row of the table.
You can simply access the columns of the same row directly:
UPDATE myTable
SET X_GAUSS = X + 1,
Y_GAUSS = Y + 2;
Related
Running PostgreSQL 12.4. I am trying to accomplish this but the syntax given there doesn't seem to be working on psql, and I could not find another approach.
I have the following data:
Table 1
ID Trait
1 X
1 Y
1 Z
2 A
2 B
Table 2
ID Traits, Listed
1
2
3
4
I would like to create the following result:
Table 2
ID Traits, Listed
1 X + Y + Z
2 A + B
Concatenating with + would be ideal, as some traits have inherent commas.
Thank you for any help!
Try something like:
update table2
SET traits = agg.t
FROM
(select id,string_agg(trait, ',') t from table1 group by id) agg
where
table2.id = agg.id;
dbfiddle
Concatenating with + would be ideal, as some traits have inherent commas.
You can use whatever delimiter you like (just change the second argument to string_agg).
I have a simple task which I cannot wrap my head around being a novice coder.
I have a data set which I am trying to manipulate.
It appears as this:
UniqueID Day Var AverageVar
1 1 X
1 2 Y
1 3 Z
2 1 A
2 2 B
2 3 C
I would like to create this new "AverageVar" variable which computes an average across the three days for each unique ID.
So, for example, the AverageVar for the first three rows I would like to create and have (X + Y + Z)/3 displayed. Is there any easy code for this in SQL or R?
SELECT * INTO newtable
FROM
(SELECT UniqueID, AVG(Var) as AverageVar
FROM table
GROUP BY UniqueID);
SELECT O.UniqueID, O.Day, O.Var, N.AverageVar
FROM oldtable O
INNER JOIN
newtable N
ON O.UniqueID = N.UniqueID;
I want to take a value from a selected column to operate the next column. For example:
SELECT CASE
WHEN ID < 4 THEN ID
ELSE 10
END
AS MY_ID,
MY_ID + 5 AS EXTRA_ID
FROM FOO
That would output for IDs 1,2,3,4,5:
MY_ID EXTRA_ID
1 6
2 7
3 8
10 15
10 15
If I do MY_ID + 5 it will complain about MY_ID not existing (it's an alias, so it makes sense) and ID + 5 will read 1+5, 2+5, 3+5, 4+5, 5+5 instead of 1+5, 2+5, 3+5, 4+10, 5+10 when it goes through the ELSE. Is it even possible to do this? I'm doing it in SSRS - Report builder, and need to operate a result that might be set to a defualt value depending on the CASE clause.
You can repeat the same CASE expression with +5 in the end for the extra_id column
SELECT CASE
WHEN ID < 4 THEN ID
ELSE 10
END
AS MY_ID,
CASE
WHEN ID < 4 THEN ID
ELSE 10
END + 5 AS EXTRA_ID
FROM FOO
An alternative is to create the extra_id column value inside SSRS using an expression
= Fields!my_id.value + 5
you cannot reuse the calculation in the same level. Using my_id in the where clause will fail as well. Either you have to calucate it multiple times, place another select around your statement or use a with statement (CTE).
Simply wrap it with another select:
SELECT t.*,
t.my_id + 5 as extra_id
FROM(Your Query) t
Derived columns are not available in the same layer they're being created. By wrapping them with another select, you make them available (that because the inner query is being processed before the outer) .
You just need a subquery to create MY_ID before doing anything with it. By creating MY_ID in the inner query the outer query can use to define new fields.
SELECT
a.MY_ID,
a.MY_ID + 5 AS EXTRA_ID
from
(SELECT
CASE
WHEN ID < 4 THEN ID
ELSE 10
END
AS MY_ID
FROM FOO) as a
i have a table name conversion and i have these below mentioned columns in it i want to multiply Length\width row elements l*w of 'dimension' values and display them in another new table
Please let me know if anything changes for the same logic in ms access
probably it is simple but i dont know exact query to solve the problem waiting for your solutions
ID area length/width dimensions **new column(L*W) here**
1 1 l 3 3*5=15
2 1 w 5
3 2 l 4
4 2 w 8
5 3 l 6
6 3 w 10
7 4 l 12
8 4 w 13
9 4 W 10
waiting for your reply
You could query the table twice: once for lengths and once for widths and then join by area and multiply the values:
select length.area, length.dimension * width.dimension
from
(select area, dimension from conversion where lenwidth = 'l') length
inner join
(select area, dimension from conversion where lenwidth = 'w') width
on length.area = width.area;
Two remarks:
I suppose that it is a typo that you have two width entries for area 4? Otherwise you would have to decide which value to take in above select statement.
It would not be a good idea to keep the old table and have a new table holding the results. What if you change a value? You would have to remember to change the result accordingly every time. So either ditch the old table or use a view instead of a new table.
Try this
select *,
dimensions*(lead(dimensions) over(order by id)) product
from table1;
Or if you want for the set of area then
select *,
case when length_width='l' and (lead(length_width) over(order by id))='w'
then dimensions*(lead(dimensions) over(order by id))
else 0
end as product
from table1;
fiddle
How can I select every thrid row from the table?
if a table has
1
2
3
4
5
6
7
8
9
records
it should pick up 3, 6,9 record. regards less what their data is.
Modulo is what you want...
Assuming contiguous values:
SELECT *
FROM Mytable
WHERE [TheColumn] Mod 3 = 0
And with gaps
SELECT *
FROM Mytable
WHERE DCount("TheColumn", "table", "TheColumn <= " & [TheColumn]) Mod 3 = 0
Edit: To exclude every 3rd record, ...Mod 3 <> 0
If its SQL you could use the row_number and over commands. see this, then where rownumvar % 3 =0 but not sure if that works in access.
Or you could put the table into a recordset and iterate through checking the index for % 3=0 if your using any kind of code.
How about a Count() on a field that has unique members. (id?) then % 3 on that.