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Full Discussion: Optimizing query
Special Forums UNIX and Linux Applications Optimizing query Post 302130209 by kahuna on Friday 3rd of August 2007 02:31:24 PM
Old 08-03-2007
Quote:
Originally Posted by matrixmadhan
Basically, with combination of using selected columns ( column1 ) and the specific rowids ( rowid ), what is the need to specify an extra condition with a separate subquery to extract column1.
Yes you are right that it makes 2 sub-selects. If you have many duplicates, then your original post may be better. But suppose you only have a single duplicate. My subquery1 returns only a single value of column1 (the duplicate), where your subquery returns many values (the non duplicates). So now I have a single value to compare against tableA where you have many values. Yes, I still have to make subquery2, but it is against a much smaller set.

Subquery2 makes sure that, for a given value of column1, we don't delete the row with the smallest rowid.

Last edited by kahuna; 08-03-2007 at 04:03 PM.. Reason: Clarification
 

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FBSQL_QUERY(3)								 1							    FBSQL_QUERY(3)

fbsql_query - Send a FrontBase query

SYNOPSIS
resource fbsql_query (string $query, [resource $link_identifier], [int $batch_size]) DESCRIPTION
Sends a $query to the currently active database on the server. If the query succeeds, you can call fbsql_num_rows(3) to find out how many rows were returned for a SELECT statement or fbsql_affected_rows(3) to find out how many rows were affected by a DELETE, INSERT, REPLACE, or UPDATE statement. PARAMETERS
o $query - The SQL query to be executed. Note The query string shall always end with a semicolon. o $ link_identifier -A FrontBase link identifier returned by fbsql_connect(3) or fbsql_pconnect(3).If optional and not specified, the function will try to find an open link to the FrontBase server and if no such link is found it will try to create one as if fbsql_connect(3) was called with no arguments. o $batch_size - RETURN VALUES
fbsql_query(3) returns TRUE (non-zero) or FALSE to indicate whether or not the query succeeded. A return value of TRUE means that the query was legal and could be executed by the server. It does not indicate anything about the number of rows affected or returned. It is perfectly possible for a query to succeed but affect no rows or return no rows. For SELECT statements, fbsql_query(3) returns a new result identifier that you can pass to fbsql_result(3). fbsql_query(3) will also fail and return FALSE if you don't have permission to access the table(s) referenced by the query. EXAMPLES
The following query is syntactically invalid, so fbsql_query(3) fails and returns FALSE: Example #1 fbsql_query(3) example <?php $result = fbsql_query("SELECT * WHERE 1=1") or die ("Invalid query"); ?> The following query is semantically invalid if my_col is not a column in the table my_tbl, so fbsql_query(3) fails and returns FALSE: Example #2 fbsql_query(3) example <?php $result = fbsql_query ("SELECT my_col FROM my_tbl;") or die ("Invalid query"); ?> SEE ALSO
fbsql_affected_rows(3), fbsql_db_query(3), fbsql_free_result(3), fbsql_result(3), fbsql_select_db(3), fbsql_connect(3). PHP Documentation Group FBSQL_QUERY(3)
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