Reply To: qSQL questions _ where clause and exec results

[rocuinneagain]

1. qSQL has some differences to q.

https://code.kx.com/q/ref/select/

“select is a qSQL query template and varies from regular q syntax.”

https://code.kx.com/q/basics/qsql/#where-phrase

“Efficient Where phrases start with their most stringent tests.”

Each where clause is it’s own expression. You can see inside [] the expression are executed left to right but within each expression the code is executed right to left.

q)[(show 2;show 1);(show 4;show 3);(show 6;show 5)];
1
2
3
4
5
6

2.

https://code.kx.com/q/basics/funsql/#group-by-column

“b is a column name. The result is a dictionary.”

https://code.kx.com/q/basics/funsql/#group-by-columns

“b is a list of column names. … returns a dictionary”

https://code.kx.com/q/basics/funsql/#group-by-a-dictionary

“b is a dictionary. Result is a dictionary in which the key is a table with columns as specified by b …”

If you parse the queries you can see that sym:sym is group by dictionary

q)parse"exec first open, last close by sym from daily where sym like \"*L\""
?
`daily
,,(like;`sym;"*L")
,`sym
`open`close!((*:;`open);(last;`close))

vs:

q)parse"exec first open, last close by sym:sym from daily where sym like \"*L\""
?
`daily
,,(like;`sym;"*L")
(,`sym)!,`sym
`open`close!((*:;`open);(last;`close))