Administration Guide

EXPLAIN_STATEMENT Table

The EXPLAIN_STATEMENT table contains the text of the SQL statement as it exists for the different levels of Explain information. The original SQL statement as entered by the user is stored in this table along with the version used (by the optimizer) to choose an access plan to satisfy the SQL statement. The latter version may bear little resemblance to the original as it may have been rewritten and/or enhanced with additional predicates as determined by the SQL Compiler.

For the definition of this table, see "EXPLAIN_STATEMENT Table Definition".

Table 131. EXPLAIN_STATEMENT Table

Column Name Data Type Nullable? Key? Description
EXPLAIN_REQUESTER CHAR(8) No PK, FK Authorization ID of initiator of this Explain request.
EXPLAIN_TIME TIMESTAMP No PK, FK Time of initiation for Explain request.
SOURCE_NAME CHAR(8) No PK, FK Name of the package running when the dynamic statement was explained or name of the source file when the static SQL was explained.
SOURCE_SCHEMA CHAR(8) No PK, FK Schema, or qualifier, of source of Explain request.
EXPLAIN_LEVEL CHAR(1) No PK Level of Explain information for which this row is relevant.
Valid values are:

O
Original Text (as entered by user)
P
PLAN SELECTION

STMTNO SMALLINT No PK Statement number within package to which this explain information is related. Set to 1 for dynamic Explain SQL statements. For static SQL statements, this value is the same as the value used for the SYSCAT.STATEMENTS catalog view.
SECTNO SMALLINT No PK Section number within package that contains this SQL statement. For dynamic Explain SQL statements, this is the section number used to hold the section for this statement at runtime. For static SQL statements, this value is the same as the value used for the SYSCAT.STATEMENTS catalog view.
QUERYNO INTEGER No No Numeric identifier for explained SQL statement. For dynamic SQL statements (excluding the EXPLAIN SQL statement) issued through CLP or CLI, the default value is a sequentially incremented value. Otherwise, the default value is the value of STMTNO for static SQL statements and 1 for dynamic SQL statements.
QUERYTAG CHAR(20) No No Identifier tag for each explained SQL statement. For dynamic SQL statements issued through CLP (excluding the EXPLAIN SQL statement), the default value is 'CLP'. For dynamic SQL statements issued through CLI (excluding the EXPLAIN SQL statement), the default value is 'CLI'. Otherwise, the default value used is blanks.
STATEMENT_TYPE CHAR(2) No No Descriptive label for type of query being explained.
Possible values are:

S
Select
D
Delete
DC
Delete where current of cursor
I
Insert
U
Update
UC
Update where current of cursor

UPDATABLE CHAR(1) No No Indicates if this statement is considered updatable. This is particularly relevant to SELECT statements which may be determined to be potentially updatable.
Possible values are:

' '
Not applicable (blank)
N
No
Y
Yes

DELETABLE CHAR(1) No No Indicates if this statement is considered deletable. This is particularly relevant to SELECT statements which may be determined to be potentially deletable.
Possible values are:

' '
Not applicable (blank)
N
No
Y
Yes

TOTAL_COST DOUBLE No No Estimated total cost (in timerons) of executing the chosen access plan for this statement; set to 0 (zero) if EXPLAIN_LEVEL is O (original text) since no access plan has been chosen at this time.
STATEMENT_TEXT CLOB(64K) No No Text or portion of the text of the SQL statement being explained. The text shown for the Plan Selection level of Explain has been reconstructed from the internal representation and is SQL-like in nature; that is, the reconstructed statement is not guaranteed to follow correct SQL syntax.
SNAPSHOT BLOB(10M) Yes No Snapshot of internal representation for this SQL statement at the Explain_Level shown.
This column is intended for use with DB2 Visual Explain. Column is set to null if EXPLAIN_LEVEL is 0 (original statement) since no access plan has been chosen at the time that this specific version of the statement is captured.
QUERY_DEGREE INTEGER No No Indicates the degree of intra-partition parallelism at the time of Explain invocation. For the original statement, this contains the directed degree of intra-partition parallelism. For the PLAN SELECTION, this contains the degree of intra-partition parallelism generated for the plan to use.

Column Name	Data Type	Nullable?	Key?	Description
EXPLAIN_REQUESTER	CHAR(8)	No	PK, FK	Authorization ID of initiator of this Explain request.
EXPLAIN_TIME	TIMESTAMP	No	PK, FK	Time of initiation for Explain request.
SOURCE_NAME	CHAR(8)	No	PK, FK	Name of the package running when the dynamic statement was explained or name of the source file when the static SQL was explained.
SOURCE_SCHEMA	CHAR(8)	No	PK, FK	Schema, or qualifier, of source of Explain request.
EXPLAIN_LEVEL	CHAR(1)	No	PK	Level of Explain information for which this row is relevant. Valid values are: O Original Text (as entered by user) P PLAN SELECTION
STMTNO	SMALLINT	No	PK	Statement number within package to which this explain information is related. Set to 1 for dynamic Explain SQL statements. For static SQL statements, this value is the same as the value used for the SYSCAT.STATEMENTS catalog view.
SECTNO	SMALLINT	No	PK	Section number within package that contains this SQL statement. For dynamic Explain SQL statements, this is the section number used to hold the section for this statement at runtime. For static SQL statements, this value is the same as the value used for the SYSCAT.STATEMENTS catalog view.
QUERYNO	INTEGER	No	No	Numeric identifier for explained SQL statement. For dynamic SQL statements (excluding the EXPLAIN SQL statement) issued through CLP or CLI, the default value is a sequentially incremented value. Otherwise, the default value is the value of STMTNO for static SQL statements and 1 for dynamic SQL statements.
QUERYTAG	CHAR(20)	No	No	Identifier tag for each explained SQL statement. For dynamic SQL statements issued through CLP (excluding the EXPLAIN SQL statement), the default value is 'CLP'. For dynamic SQL statements issued through CLI (excluding the EXPLAIN SQL statement), the default value is 'CLI'. Otherwise, the default value used is blanks.
STATEMENT_TYPE	CHAR(2)	No	No	Descriptive label for type of query being explained. Possible values are: S Select D Delete DC Delete where current of cursor I Insert U Update UC Update where current of cursor
UPDATABLE	CHAR(1)	No	No	Indicates if this statement is considered updatable. This is particularly relevant to SELECT statements which may be determined to be potentially updatable. Possible values are: ' ' Not applicable (blank) N No Y Yes
DELETABLE	CHAR(1)	No	No	Indicates if this statement is considered deletable. This is particularly relevant to SELECT statements which may be determined to be potentially deletable. Possible values are: ' ' Not applicable (blank) N No Y Yes
TOTAL_COST	DOUBLE	No	No	Estimated total cost (in timerons) of executing the chosen access plan for this statement; set to 0 (zero) if EXPLAIN_LEVEL is O (original text) since no access plan has been chosen at this time.
STATEMENT_TEXT	CLOB(64K)	No	No	Text or portion of the text of the SQL statement being explained. The text shown for the Plan Selection level of Explain has been reconstructed from the internal representation and is SQL-like in nature; that is, the reconstructed statement is not guaranteed to follow correct SQL syntax.
SNAPSHOT	BLOB(10M)	Yes	No	Snapshot of internal representation for this SQL statement at the Explain_Level shown. This column is intended for use with DB2 Visual Explain. Column is set to null if EXPLAIN_LEVEL is 0 (original statement) since no access plan has been chosen at the time that this specific version of the statement is captured.
QUERY_DEGREE	INTEGER	No	No	Indicates the degree of intra-partition parallelism at the time of Explain invocation. For the original statement, this contains the directed degree of intra-partition parallelism. For the PLAN SELECTION, this contains the degree of intra-partition parallelism generated for the plan to use.

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