5.6 How to process subqueries
There are two types of subquery processing methods:
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Methods for processing subqueries that do not contain an external reference column
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Methods for processing subqueries that contain an external reference column
This section explains these subquery processing methods and their characteristics.
Note that you can check which processing method was used by viewing the access path after the SQL statement is executed. For details about access paths, see the following subsections:
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How to check access paths
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Information that is displayed as access paths
See (2) Subquery processing methods in 6.1.4 Information displayed in the tree view.
For details about external reference columns, see Specification format and rules for subqueries in the manual HADB SQL Reference.