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How to convert below functional select query to a QSQL format.
Hi All,
I am new to kdb and wanted to prepare a report containing information of how many rows are seen in variable rdb tables. For this I see we can get that via below functional query that provide us dictionary with table name and count(tables[] ! { count value (? ; x ; () ; 0b ; () ) } each tables[]Above gives me the expected output, but I wanted to perform this via qsql for my understanding. But this gives me the error.
tables[] ! ( { count value ( select from x ) } each tables [] )I tried to use the implicit argument x and passed it to function which then count the number of rows inside the lambda function and then tried passing it parameter each tables [] which results into an error. How can I debug this error with some meaningful error thrown and what would be right way to do it ?
Thanks in advance.
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1 Reply
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The first example line you show is creating parse trees and then evaluating them with
valuehttps://code.kx.com/q/basics/parsetrees/
You then replace the parse tree with a qsql statement which evaluates, this means you no longer need value:
tables[]!{count select from x} each tables[]The debugger uses
^to show you exactly where the error is thrown// ^ tells us the error happened when value was run
q)tables[] ! ( { count value ( select from x ) } each tables [] ) 'type [2] { count value ( select from x ) } ^ q))select from x // select from x returns a table a - 1 2 3 q))value select from x //Running value on a table is not a valid command 'type [4] value select from x ^ q))count select from x //We should run count directly on the returned table 3
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