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augustin_p
Starting Member
21 Posts |
 Posted - 2002-04-16 : 04:51:07
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| What's the difference between using 'left join ' keyword and '*=' ?For example The below query which is possible using 'join' keyword does not seem to be possible using '*=' symbols.select columnnlist from table1 t1 left join table2 t2 on t1.columname=t2.columnname inner join table3 t3 on t2.columname=t3.columnname If the same is written using '*=' likeselect columnlist from table1 t1, table2 t2, table3 t3where t1.columnname *= t2.Columnname and t2.columnname = t3.columnnameIt gives an error "The table 'Table2' is an inner member of an outer-join clause. This is not allowed if the table also participates in a regular join clause."i would like to know the difference between the way the above 2 queries executes.Thanks,prasanna |
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robvolk
Most Valuable Yak
15732 Posts |
Posted - 2002-04-16 : 08:05:31
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| The *= syntax is obsolete in SQL Server. It still works most of the time, but its days are numbered. One of the reasons it's obsolete is that it doesn't allow you to mix join types, like you are trying to do in this query. The JOIN syntax is not only the ANSI standard, but it also separates the JOIN logic from the WHERE logic, where the *= syntax does not separate the two.The sooner you move your queries to the ANSI JOIN syntax, the better. At some point, when you upgrade your SQL Server, the older syntax will simply stop working, and you'll have to convert them anyway. |
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Nazim
A custom title
1408 Posts |
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Joins