Force Table Scan in SQL Server/Sybase

August 7, 2010 By Leave a Comment

When extracting whole tables or large recordsets (say, at least 80% of the table), it is better to use Full Table Scan than use index. Full scan is more efficient in this case because it no longer need to search through the index for each record. It doesn’t need to because the whole table is going to be extracted anyways.
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Filed Under: SQL Server, Sybase Tagged With: , ,

Oracle NVL Equivalent in MySQL

December 28, 2009 By 2 Comments

Here’s the MySQL equivalent of Oracle’s NVL and MSSQL/Sybase’s ISNULL functions.

Syntax


IFNULL(expr1,expr2)

Usage

If expr1 is not NULL, IFNULL() returns expr1; otherwise it returns expr2. Take note that IFNULL() returns a numeric or string value, depending on the context in which it is used. I haven’t used it for other data types yet but I reckon it would have the same results. That is to return the same data type as that of expr1. Another important thing to remember is that expr1 and expr2 should have the same data type

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Filed Under: MySQL Tagged With: , , , ,