Oracle8i SQL Reference Release 2 (8.1.6) A76989-01 |
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SQL Statements (continued), 8 of 11
This statement lets you
For most statistics collection purposes, Oracle Corporation recommends that you use the DBMS_STATS
package. That package lets you collect statistics in parallel, collect global statistics for partitioned objects, and fine tune your statistics collection in other ways. See Oracle8i Supplied PL/SQL Packages Reference for more information on this package.
However, you can use this statement for any of the purposes described in this section, and you must use this statement (rather than the DBMS_STATS
package) for the following purposes:
VALIDATE
or LIST
CHAINED
ROWS
clauses
The schema object to be analyzed must be local, and it must be in your own schema or you must have the ANALYZE
ANY
system privilege.
If you want to list chained rows of a table or cluster into a list table, the list table must be in your own schema, or you must have INSERT
privilege on the list table, or you must have INSERT
ANY
TABLE
system privilege.
If you want to validate a partitioned table, you must have INSERT
privilege on the table into which you list analyzed rowids, or you must have INSERT
ANY
TABLE
system privilege.
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is the schema containing the index, table, or cluster. If you omit schema, Oracle assumes the index, table, or cluster is in your own schema. |
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identifies an index to be analyzed (if no for_clause is used). |
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Oracle collects the following statistics for an index (statistics marked with an asterisk are always computed exactly):
Index statistics appear in the data dictionary views |
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For a domain index, this statement invokes the user-defined statistics collection function specified in the statistics type associated with the index (see "ASSOCIATE STATISTICS"). If no statistics type is associated with the domain index, the statistics type associated with its indextype is used. If no statistics type exists for either the index or its indextype, no user-defined statistics are collected. User-defined index statistics appear in the data dictionary views
Restriction: You cannot analyze a domain index that is marked See Also: "CREATE INDEX" for more information on domain indexes. |
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identifies a table to be analyzed. When you collect statistics for a table, Oracle also automatically collects the statistics for each of the table's indexes and domain indexes, provided that no for_clauses are used. When you analyze a table, Oracle collects statistics about expressions occurring in any function-based indexes as well. Therefore, be sure to create function-based indexes on the table before analyzing the table. See Also: "CREATE INDEX" for more information about function-based indexes. |
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When analyzing a table, Oracle skips all domain indexes marked
Table statistics, including the status of domain indexes, appear in the data dictionary views |
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Oracle collects the following statistics for a table (statistics marked with an asterisk are always computed exactly):
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Restrictions:
See Also: "ASSOCIATE STATISTICS". |
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specifies that statistics will be gathered for partition or subpartition. You cannot use this clause when analyzing clusters.
If you specify |
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identifies a cluster to be analyzed. When you collect statistics for a cluster, Oracle also automatically collects the statistics for all the cluster's tables and all their indexes, including the cluster index. |
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These statistics appear in the data dictionary views |
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computes exact statistics about the analyzed object and stores them in the data dictionary. When you analyze a table, both table and column statistics are collected. |
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estimates statistics about the analyzed object and stores them in the data dictionary. |
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Both computed and estimated statistics are used by the Oracle optimizer to choose the execution plan for SQL statements that access analyzed objects. These statistics may also be useful to application developers who write such statements. For information on how these statistics are used, see Oracle8i Designing and Tuning for Performance. |
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specifies the amount of data from the analyzed object Oracle samples to estimate statistics. If you omit this parameter, Oracle samples 1064 rows.
The default sample value is adequate for tables up to a few thousand rows. If your tables are larger, specify a higher value for |
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causes Oracle to sample integer rows of the table or cluster or integer entries from the index. The integer must be at least 1. |
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causes Oracle to sample integer percent of the rows from the table or cluster or integer percent of the index entries. The integer can range from 1 to 99. |
for_clause |
specifies whether an entire table or index, or just particular columns, will be analyzed. The following clauses apply only to the |
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restricts the statistics collected to only table statistics rather than table and column statistics. |
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restricts the statistics collected to only column statistics for the specified columns and scalar object attributes, rather than for all columns and attributes; attribute specifies the qualified column name of an item in an object. |
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collects column statistics for all columns and scalar object attributes. |
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collects column statistics for all indexed columns in the table. |
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Column statistics can be based on the entire column or can use a histogram by specifying SIZE Oracle collects the following column statistics: See Also: Oracle8i Designing and Tuning for Performance and "Histogram Examples" for more information on histograms. |
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Column statistics appear in the data dictionary views |
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Note: The |
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If a user-defined statistics type has been associated with any columns, the for_clause collects user-defined statistics using that statistics type. If no statistics type is associated with a column, Oracle checks to see if any statistics type has been associated with the type of the column, and uses that statistics type. If no statistics type has been associated with either the column or its user-defined type, no user-defined statistics are collected. User-defined column statistics appear in the data dictionary views |
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If you want to collect statistics on both the table as a whole and on one or more columns, be sure to generate the statistics for the table first, and then for the columns. Otherwise, the table-only ANALYZE will overwrite the histograms generated by the column ANALYZE TABLE emp ESTIMATE STATISTICS; ANALYZE TABLE emp ESTIMATE STATISTICS FOR ALL COLUMNS; |
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specifies that all indexes associated with the table will be analyzed. |
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specifies that all local index partitions are analyzed. You must specify the keyword |
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specifies the maximum number of partitions in the histogram. The default value is 75, minimum value is 1, and maximum value is 254. |
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deletes any statistics about the analyzed object that are currently stored in the data dictionary. Use this statement when you no longer want Oracle to use the statistics. When you use this clause on a table, Oracle also automatically removes statistics for all the table's indexes. When you use this clause on a cluster, Oracle also automatically removes statistics for all the cluster's tables and all their indexes, including the cluster index. |
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If user-defined column or index statistics were collected for an object, Oracle also removes the user-defined statistics by invoking the statistics deletion function specified in the statistics type that was used to collect the statistics. |
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validates the REFs in the specified table, checks the rowid portion in each REF, compares it with the true rowid, and corrects, if necessary. You can use this clause only when analyzing a table. |
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sets to |
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Note: If the owner of the table does not have |
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validates the structure of the analyzed object. The statistics collected by this clause are not used by the Oracle optimizer, as are statistics collected by the
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Validating the structure of an object prevents If Oracle encounters corruption in the structure of the object, an error message is returned to you. In this case, drop and re-create the object. |
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specifies a table into which Oracle lists the rowids of the partitions whose rows do not collate correctly. If you omit schema, Oracle assumes the list is in your own schema. If you omit this clause altogether, Oracle assumes that the table is named |
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validates the structure of the indexes associated with the table or cluster. If you use this clause when validating a table, Oracle also validates the table's indexes. If you use this clause when validating a cluster, Oracle also validates all the clustered tables' indexes, including the cluster index. |
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If you use this clause to validate an enabled (but previously disabled) function-based index, validation errors may result. In this case, you must rebuild the index. |
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identifies migrated and chained rows of the analyzed table or cluster. You cannot use this clause when analyzing an index. |
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specifies a table into which Oracle lists the migrated and chained rows. If you omit schema, Oracle assumes the list table is in your own schema. If you omit this clause altogether, Oracle assumes that the table is named |
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You can create the
If you create your own chained-rows table, it must follow the format prescribed by one of these two scripts. See Oracle8i Migration for compatibility issues related to the use of these scripts. |
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Note: If you are analyzing index-organized tables based on primary keys (rather than universal rowids), you must create a separate chained-rows table for each index-organized table to accommodate its primary-key storage. Use the SQL scripts
For information on the SQL scripts, see the |
The following statement estimates statistics for the CUST_HISTORY
table and all of its indexes:
ANALYZE TABLE cust_history ESTIMATE STATISTICS;
The following statement deletes statistics about the CUST_HISTORY
table and all its indexes from the data dictionary:
ANALYZE TABLE cust_history DELETE STATISTICS;
The following statement creates a 10-band histogram on the SAL
column of the EMP
table:
ANALYZE TABLE emp COMPUTE STATISTICS FOR COLUMNS sal SIZE 10;
You can also collect histograms for a single partition of a table. The following statement analyzes the EMP
table partition P1
:
ANALYZE TABLE emp PARTITION (p1) COMPUTE STATISTICS;
The following statement validates the structure of the index PARTS_INDEX
:
ANALYZE INDEX parts_index VALIDATE STRUCTURE;
The following statement analyzes the EMP
table and all of its indexes:
ANALYZE TABLE emp VALIDATE STRUCTURE CASCADE;
For a table, the VALIDATE REF UPDATE
clause verifies the REFs in the specified table, checks the rowid portion of each REF, and then compares it with the true rowid. If the result is an incorrect rowid, the REF is updated so that the rowid portion is correct.
The following statement validates the REFs in the EMP
table:
ANALYZE TABLE emp VALIDATE REF UPDATE;
The following statement analyzes the ORDER_CUSTS
cluster, all of its tables, and all of their indexes, including the cluster index:
ANALYZE CLUSTER order_custs VALIDATE STRUCTURE CASCADE;
The following statement collects information about all the chained rows of the table ORDER_HIST
:
ANALYZE TABLE order_hist LIST CHAINED ROWS INTO cr;
The preceding statement places the information into the table CR
. You can then examine the rows with this query:
SELECT * FROM cr; OWNER_NAME TABLE_NAME CLUSTER_NAME HEAD_ROWID TIMESTAMP ---------- ---------- ------------ ------------------ --------- SCOTT ORDER_HIST AAAAZzAABAAABrXAAA 15-MAR-96
The following statement calculates statistics for a scalar object attribute:
ANALYZE TABLE emp COMPUTE STATISTICS FOR COLUMNS addr.street;
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