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EXPLAIN Statement
The EXPLAIN statement helps you to review query execution plans. You can use the EXPLAIN
statement anywhere you can execute other Neoview database statements (for example, SELECT).
For information about the Neoview Command Interface (NCI), see the Neoview Command Interface
(NCI) Guide. For more information on the EXPLAIN function, see
NOTE:
Formatting changes to the EXPLAIN output data might occur in the future. If so, you
might need to modify any scripts that parse the output of the command.
The syntax for the EXPLAIN statement supports four output options.
options.
Table 2-3 EXPLAIN Statement Options
Syntax
OPTIONS 'f'
OPTIONS 'n'
OPTIONS 'e'
OPTIONS 'm'
Plans displayed by the EXPLAIN statement OPTIONS 'n', 'e', and 'f' are ordered from top (root
operator) to bottom (leaf operators). The machine-readable format (option 'm') orders plans from
bottom (leaf operators) to top (root operator).
For detailed information about the operators in the query execution plan, see the Neoview Query
Guide.
Syntax Description of EXPLAIN
EXPLAIN [OPTIONS {'f' | 'n' | 'e' | 'm'}] {FOR QID qid | query-text | prepared-stmt-name}
f
formatted. See
n
normal user (default setting). See
e
expert user. See
m
machine readable format. See
qid
a delimited identifier or regular identifier, which represents the query ID. This example
shows the query ID, which contains lowercase characters, as a delimited identifier:
QID "MXID01001011194212103659400053369000000085905admin00_2605_S1"
query-text
a DML statement such as SELECT * FROM T3.
124
SQL Statements
Option Type
Formatted
Normal user
Expert user
Machine readable
"Formatted [OPTIONS 'f'] Considerations" (page
"Normal User [OPTIONS 'n'] Considerations" (page
"Expert User [OPTIONS 'e'] Considerations" (page
"Machine-Readable [OPTIONS 'm'] Considerations" (page
"EXPLAIN Function" (page
Purpose
Provides the simple, basic information contained in the
query execution plan. This information is formatted for
readability and limited to 79 characters (one line) per
operator.
Provides the most important information contained in the
query execution plan. This information is formatted for
readability and is the default output format.
Provides all information contained in the query execution
plan. This information is formatted for readability.
Provides all information contained in the query execution
plan. This information is formatted for machine readability
(easy to parse with software tools). Same format as EXPLAIN
function (see
"EXPLAIN Function" (page
Table 2-3
summarizes the
401)).
125).
126).
128).
401).
130).
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