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Description
| - describe SQL statement compilation The explain function compiles a SQL statement and returns a description of that compilation as a result set, return value or parse tree. The result set consists of one VARCHAR column with one line of the description in each row. Any given line may be quite long, even several hundred characters. The output is not a complete disassembly of the query graph, but it is detailed enough to show the join order, the sub-query structure, and the order of evaluation of query predicates, as well as the splitting of a distributed VDB query over different data sources. The optional cursor type can be one of the SQL_CURSOR_ constants, or one of the special values listed below. The default is 0, for FORWARD ONLY. The special values each have special effect, as listed. If the statement is a SELECT and the cursor type is not FORWARD ONLY, the auxiliary SQL statements used by the cursor implementation are shown.
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Creator
| - virtuoso.docs@openlinksw.com
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Date
| - 2013-07-11T21:22:54Z
- 2015-02-05T21:17:51Z
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Title
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type
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content:encoded
| - describe SQL statement compilation
The explain function compiles a SQL statement and returns a description
of that compilation as a result set, return value or parse tree. The result set consists of one
VARCHAR column with one line of the description in each row. Any given
line may be quite long, even several hundred characters.
The output is not a complete disassembly of the query graph, but it
is detailed enough to show the join order, the sub-query structure,
and the order of evaluation of query predicates, as well as the
splitting of a distributed VDB query over different data sources.
The optional cursor type can be one of the SQL_CURSOR_<xx> constants,
or one of the special values listed below. The default is 0, for
FORWARD ONLY. The special values each have special effect, as listed.
If the statement is a SELECT and the cursor type is not FORWARD ONLY,
the auxiliary SQL statements used by the cursor implementation are
shown.
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