Carlos Savoretti wrote:
Hello all:
I need to make certain operations like this:
select tbl_no as 'Number' , @sal1 := tbl_db - tbl_hb + @sal1 as 'Total'
I'm using the C API; so I make it through mysql_query()
Problem is than having `tbl_db' and 'tbl_hb' with certain values no
operation is carried out, and `Total' is NULL.
What am I doing bad ?
Please, help me
Thanks all
Carlos Savoretti [EMAIL PROTECTED]
@sal1 is NULL until you assign it a value. Your assignment is self-referential.
@sal1 := tbl_db - tbl_hb + @sal1
On the first pass, then, that's
@sal1 := tbl_db - tbl_hb + NULL
Anything plus NULL is NULL, so you get
@sal1 := tbl_db - tbl_hb + NULL
on every subsequent pass, as well.
You need to start with
SET @sal1 = 0;
first.
Michael
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