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How I do query like this ?
select Distinct Station , Slot , SubSlot, CompID , CompName
from DeviceTrace as DT DT.DeviceID = '1339759958'
inner join CompList as CL
where and DT.CompID = CL.CompID
I need to do DT.DeviceID = '1339759958' before I start with the inner join.
I work with sql server.
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You join two tables by creating a relationship in the WHERE clause between at least one column from one table and at least one column from another. The join creates a temporary composite table where each pair of rows (one from each table) that satisfies the join condition is linked to form a single row.
The rows selected by a query are filtered first by the FROM clause join conditions, then the WHERE clause search conditions, and then the HAVING clause search conditions.
The first two are types of explicit joins and the last is an implicit join. An explicit JOIN explicitly tells you how to JOIN the data by specifying the type of JOIN and the join condition in the ON clause. An Implicit JOIN does not specify the JOIN type and use the WHERE clause to define the join condition.
SQL's from clause selects and joins your tables and is the first executed part of a query. This means that in queries with joins, the join is the first thing to happen.
I find it difficult to believe that it makes any difference. The query optimiser should apply the predicate before the join if it calculates that it is more efficient to do so. The only circumstance where you might need to do this is when the optimiser makes an erroneous choice (for inner joins at least -- there are valid cases for outer joins).
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