The REFRESH TABLE statement refreshes the data in a materialized query table. The statement deletes all rows in the materialized query table, executes the fullselect in the table definition to recalculate the data from the tables specified in the fullselect, inserts the calculated result into the materialized query table, and updates the catalog for the refresh timestamp and cardinality of the table. The table can exist at the current server or at any DB2 subsystem with which the current server can establish a connection.
This command is only implemented syntactically in the XDB Server operating environment.
Invocation
This statement can be embedded in an application program or issued interactively. It is an executable statement that can be dynamically prepared only if DYNAMICRULES run behavior is implicitly or explicitly specified.
Authorization
The privilege set for REFRESH TABLE must include at least one of the following authorities:
- Ownership of the materialized query table
- DBADM or DBCTRL authority on the database that contains the materialized query table
- SYSADM or SYSCTRL authority
If the statement is embedded in an application program, the privilege set is the privileges that are held by the authorization ID of the owner of the plan or package. If the statements dynamically prepared, the privilege set is determined by the DYNAMICRULES behavior in effect (run, bind, define, or invoke).
Syntax
Bold text indicates clauses or options that are supported only
syntactically.
REFRESH TABLE table-name [QUERYNO integer]
table-name
Identifies the table to be refreshed. The name must identify a materialized query table. REFRESH TABLE evaluates the fullselect in the materialized-query-definition clause to refresh the table. The isolation level for the fullselect is the isolation level of the materialized query table recorded when CREATE TABLE or ALTER TABLE was issued.
QUERYNO
integer
Specifies the number to be used for this SQL statement in EXPLAIN output and trace records. The number is used for the QUERYNO column of the plan table for the rows that contain information about this SQL statement. This number is also used in the QUERYNO column of the SYSIBM.SYSSTMT and SYSIBM.SYSPACKSTMT catalog tables.
If the clause is omitted, the number associated with the SQL statement is the statement number assigned during precompilation. Thus, if the application program is changed and then precompiled, that statement number might change.
Note:
- Automatic query rewrite using materialized query tables is not attempted for the fullselect in the materialized query table definition during the processing of REFRESH TABLE statement.
- After successful execution of a REFRESH TABLE statement, the SQLCA field SQLERRD(3) will contain the number of rows inserted into the materialized query table.
- The EXPLAIN output for REFRESH TABLE
table-name is the same as the EXPLAIN output for INSERT INTO
table-name fullselect where
fullselect is from the materialized query table definition.
- The REFRESH TABLE statement is supported over DRDA protocol, but not supported over DB2 private protocol.
- If the materialized query table has a security label column, the REFRESH TABLE statement does not do any checking for multilevel security with row-level granularity when it deletes and repopulates the data in the table by executing the fullselect. Instead, DB2 performs the checking for multilevel security with row-level granularity when the materialized query table is exploited in automatic query rewrite or is used directly.
