DSN_QUERY_TABLE

The query table, DSN_QUERY_TABLE, contains information about a SQL statement, and displays the statement before and after query transformation.

Begin program-specific programming interface information.

Unlike other EXPLAIN tables, rows in DSN_QUERY_TABLE are not populated for static SQL statements at BIND or REBIND with the EXPLAIN(YES) option.

Recommendation: Start of change

Do not manually insert data into system-maintained EXPLAIN tables, and use care when deleting obsolete EXPLAIN table data. The data is intended to be manipulated only by the DB2® EXPLAIN function and optimization tools. Certain optimization tools depend on instances of the various EXPLAIN tables. Be careful not to delete data from or drop instances EXPLAIN tables that are created for these tools. End of change

Qualifiers

Your subsystem or data sharing group can contain more than one of these tables:

'SYSIBM': One instance of this table can be created with the SYSIBM qualifier. DB2 and SQL optimization tools might use the table and the data that it contains. The table is created when you run job DSNTIJSG when you install or migrate DB2.
'user-ID': You can create additional instances of EXPLAIN tables that are qualified by user ID. These tables are populated with statement cost information when you issue the EXPLAIN statement or bind. They are also populated when you specify EXPLAIN(YES) or EXPLAIN(ONLY) in a BIND or REBIND command. SQL optimization tools might also create EXPLAIN tables that are qualified by a user ID. You can find the SQL statement for creating an instance of these tables in member DSNTESC of the SDSNSAMP library.

Sample CREATE TABLE statement

You can find a sample CREATE TABLE statement for each EXPLAIN table in member DSNTESC of the prefix.SDSNSAMP library.

Column descriptions

The following table describes the columns of DSN_QUERY_TABLE.

Table 1. DSN_QUERY_TABLE description
Column name	Data type	Description
QUERYNO	INTEGER NOT NULL	A number that identifies the statement that is being explained. The origin of the value depends on the context of the row: For rows produced by EXPLAIN statements The number specified in the QUERYNO clause, which is an optional part of the SELECT, INSERT, UPDATE, MERGE, and DELETE statement syntax. For rows not produced by EXPLAIN statements DB2 assigns a number that is based on the line number of the SQL statement in the source program. When the values of QUERYNO are based on the statement number in the source program, values that exceed 32767 are reported as 0. However, in certain rare cases, the value is not guaranteed to be unique. When the SQL statement is embedded in a compiled SQL function or native SQL procedure, if the QUERYNO clause is specified, its value is used by DB2. Otherwise DB2 assigns a number based on the line number of the SQL statement in the compiled SQL function or native SQL procedure.
TYPE	CHAR(8) NOT NULL	The type of the data in the NODE_DATA column.
QUERY STAGE	CHAR(8) NOT NULL WITH DEFAULT	The stage during query transformation when this row is populated.
SEQNO	NOT NULL	The sequence number for this row if NODE_DATA exceeds the size of its column.
NODE_DATA	CLOB(2M)	The XML data containing the SQL statement and its query block, table, and column information.
EXPLAIN_TIME	TIMESTAMP	The EXPLAIN timestamp.
QUERY_ROWID	ROWID NOT NULL GENERATED ALWAYS	The ROWID of the statement.
GROUP MEMBER	VARCHAR(24) NOT NULL	The member name of the DB2 subsystem that executed EXPLAIN. The column is blank if the DB2 subsystem was not in a data sharing environment when EXPLAIN was executed.
HASHKEY	INTEGER NOT NULL	The hash value of the contents in NODE_DATA
HAS_PRED	CHAR(1) NOT NULL	When NODE_DATA contains an SQL statement, this column indicates if the statement contains a parameter marker literal, non-parameter marker literal, or no predicates.
SECTNOI	INTEGER NOT NULL WITH DEFAULT	The section number of the statement. The value is taken from the same column in SYSPACKSTMT or SYSSTMT tables and can be used to join tables to reconstruct the access path for the statement. This column is applicable only for static statements. The default value of -1 indicates EXPLAIN information that was captured in DB2 9 or earlier.
APPLNAME	VARCHAR(24) NOT NULL WITH DEFAULT	The name of the application plan for the row. Applies only to embedded EXPLAIN statements that are executed from a plan or to statements that are explained when binding a plan. A blank indicates that the column is not applicable. When the SQL statement is embedded in a compiled SQL function or native SQL procedure, this column is not used, and is blank.
PROGNAME	VARCHAR(128) NOT NULL WITH DEFAULT	The name of the program or package containing the statement being explained. Applies only to embedded EXPLAIN statements and to statements explained as the result of binding a plan or package. A blank indicates that the column is not applicable. When the SQL statement is embedded in a compiled SQL function or native SQL procedure, this column indicates the specific name of the compiled SQL function or native SQL procedure.
COLLID	VARCHAR(128) NOT NULL WITH DEFAULT	The collection ID: 'DSNDYNAMICSQLCACHE' The row originates from the dynamic statement cache 'DSNEXPLAINMODEYES' The row originates from an application that specifies YES for the value of the CURRENT EXPLAIN MODE special register. 'DSNEXPLAINMODEEXPLAIN' The row originates from an application that specifies EXPLAIN for the value of the CURRENT EXPLAIN MODE special register. When the SQL statement is embedded in a compiled SQL function or native SQL procedure, this column indicates the schema name of the compiled SQL function or native SQL procedure.
VERSION	VARCHAR(122) NOT NULL WITH DEFAULT	The version identifier for the package. Applies only to an embedded EXPLAIN statement executed from a package or to a statement that is explained when binding a package. A blank indicates that the column is not applicable. When the SQL statement is embedded in a compiled SQL function or native SQL procedure, this column indicates the version identifier of the compiled SQL function or native SQL procedure.

End program-specific programming interface information.