對於Oracle analyze table的使用總結 . 對於Oracle analyze table的使用總結 .

對於Oracle analyze table的使用總結 . 對於Oracle analyze table的使用總結 .

analyze table 通常能夠指定分析： 表，全部字段，全部索引字段，全部索引。 若不指定則所有都分析。

SQL> analyze table my_table compute statistics;  

SQL> analyze table my_table compute statistics for table for all indexes for all columns;   

SQL> analyze table my_table compute statistics for table for all indexes for all indexed columns;  

其中：

SQL> analyze table my_table compute statistics;  

等價於：

SQL> analyze table my_table compute statistics for table for all indexes for all columns;   

sample:

analyze table t1 compute statistics for table;
analyze table t2 compute statistics for all columns;
analyze table t3 compute statistics for all indexed columns;

analyze table t5 compute statistics for all indexes;

analyze table t4 compute statistics;     (不指定）

另外，能夠刪除分析數據：

SQL> analyze table my_table delete statistics;

SQL> analyze table my_table delete statistics for table for all indexes for all indexed columns;  

http://wfly2004.blog.163.com/blog/static/1176427201042891042233/

首先建立四個臨時表t1,t2,t3,t4,和他們相對應的索引
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代碼:
create table t1 as select * from user_objects;
create table t2 as select * from user_objects;
create table t3 as select * from user_objects;
create table t4 as select * from user_objects;
create unique index pk_t1_idx on t1(object_id);
create unique index pk_t2_idx on t2(object_id);
create unique index pk_t3_idx on t3(object_id);
create unique index pk_t4_idx on t4(object_id);

查看這個時候各個表對應的數據庫統計信息(表,字段,索引)
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代碼:
--查看錶的統計信息
select table_name,num_rows,blocks,empty_blocks from user_table where table_names in ('T1','T2','T3','T4');
TABLE_NAME        NUM_ROWS        BLOCKS        EMPTY_BLOCKS
T1                       
T2                       
T3                       
T4                       

--查看字段的統計信息
select table_name,column_name,num_distinct,low_value,high_value,density from user_tab_columns where table_name in ('T1','T2','T3','T4');
TABLE_NAME        COLUMN_NAME        NUM_DISTINCT        LOW_VALUE        HIGH_VALUE        DENSITY
T1        OBJECT_NAME                               
T1        SUBOBJECT_NAME                               
T1        OBJECT_ID                               
T1        DATA_OBJECT_ID                               
T1        OBJECT_TYPE                               
T1        CREATED                               
T1        LAST_DDL_TIME                               
T1        TIMESTAMP                               
T1        STATUS                               
T1        TEMPORARY                               
T1        GENERATED                               
T1        SECONDARY                               
T2        OBJECT_NAME                               
T2        SUBOBJECT_NAME                               
T2        OBJECT_ID                               
T2        DATA_OBJECT_ID                               
T2        OBJECT_TYPE                               
T2        CREATED                               
T2        LAST_DDL_TIME                               
T2        TIMESTAMP                               
T2        STATUS                               
T2        TEMPORARY                               
T2        GENERATED                               
T2        SECONDARY                               
T3        OBJECT_NAME                               
T3        SUBOBJECT_NAME                               
T3        OBJECT_ID                               
T3        DATA_OBJECT_ID                               
T3        OBJECT_TYPE                               
T3        CREATED                               
T3        LAST_DDL_TIME                               
T3        TIMESTAMP                               
T3        STATUS                               
T3        TEMPORARY                               
T3        GENERATED                               
T3        SECONDARY                               
T4        OBJECT_NAME                               
T4        SUBOBJECT_NAME                               
T4        OBJECT_ID                               
T4        DATA_OBJECT_ID                               
T4        OBJECT_TYPE                               
T4        CREATED                               
T4        LAST_DDL_TIME                               
T4        TIMESTAMP                               
T4        STATUS                               
T4        TEMPORARY                               
T4        GENERATED                               
T4        SECONDARY                               

--查看索引的統計信息
select table_name,index_name,blevel,leaf_blocks,distinct_keys,
        avg_leaf_blocks_per_key avg_leaf_blocks,avg_data_blocks_per_key avg_data_blocks,clustering_factor,num_rows
from user_indexes where table_name in ('T1','T2','T3','T4');
TABLE_NAME        INDEX_NAME        BLEVEL        LEAF_BLOCKS        DISTINCT_KEYS        AVG_LEAF_BLOCKS        AVG_DATA_BLOCKS        CLUSTERING_FACTOR        NUM_ROWS
T1        PK_T1_IDX                                                       
T2        PK_T2_IDX                                                       
T3        PK_T3_IDX                                                       
T4        PK_T4_IDX          

如今咱們分別對這個表作不一樣形式的analyze table處理
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代碼:
analyze table t1 compute statistics for table;
analyze table t2 compute statistics for all columns;
analyze table t3 compute statistics for all indexed columns;
analyze table t4 compute statistics;

咱們再回頭看看這是的oracle數據庫對於各類統計信息
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代碼:
--這是對於表的統計信息
select table_name,num_rows,blocks,empty_blocks from user_tables where table_name in ('T1','T2','T3','T4');
TABLE_NAME        NUM_ROWS        BLOCKS        EMPTY_BLOCKS
T1        3930        55        1
T2                       
T3                       
T4        3933        55        1
--咱們能夠據此得出結論,只有咱們在analyze table命令中指定了for table或者不指定任何參數的時候,oracle數據庫纔會給咱們統計基於表的統計信息

--這是對於表中字段的統計信息
select table_name,column_name,num_distinct,low_value,high_value,density from user_tab_columns where table_name in ('T1','T2','T3','T4');
TABLE_NAME        COLUMN_NAME        NUM_DISTINCT        LOW_VALUE        HIGH_VALUE        DENSITY
T1        OBJECT_NAME                               
T1        SUBOBJECT_NAME                               
T1        OBJECT_ID                               
T1        DATA_OBJECT_ID                               
T1        OBJECT_TYPE                               
T1        CREATED                               
T1        LAST_DDL_TIME                               
T1        TIMESTAMP                               
T1        STATUS                               
T1        TEMPORARY                               
T1        GENERATED                               
T1        SECONDARY                               
T2        OBJECT_NAME        3823        41423030        D3F1BBB736D4C2B7DDCFFABBA7C7E5B5A5        .000270447891062615
T2        SUBOBJECT_NAME        77        503031        52455354        .012987012987013
T2        OBJECT_ID        3930        C304062D        C30F4619        .000254452926208651
T2        DATA_OBJECT_ID        3662        C304062D        C30F4619        .000273074822501365
T2        OBJECT_TYPE        15        4441544142415345204C494E4B        56494557        .000127194098193844
T2        CREATED        3684        7867081E111F33        7868071211152F        .000547559423988464
T2        LAST_DDL_TIME        3574        7867081E11251B        7868071211152F        .000565522924083892
T2        TIMESTAMP        3649        323030332D30382D33303A31363A33303A3530        323030342D30372D31383A31363A32303A3436        .000559822349362313
T2        STATUS        2        494E56414C4944        56414C4944        .000127194098193844
T2        TEMPORARY        2        4E        59        .000127194098193844
T2        GENERATED        2        4E        59        .000127194098193844
T2        SECONDARY        2        4E        59        .000127194098193844
T3        OBJECT_NAME                               
T3        SUBOBJECT_NAME                               
T3        OBJECT_ID        3931        C304062D        C30F461A        .000254388196387688
T3        DATA_OBJECT_ID                               
T3        OBJECT_TYPE                               
T3        CREATED                               
T3        LAST_DDL_TIME                               
T3        TIMESTAMP                               
T3        STATUS                               
T3        TEMPORARY                               
T3        GENERATED                               
T3        SECONDARY                               
T4        OBJECT_NAME        3825        41423030        D3F1BBB736D4C2B7DDCFFABBA7C7E5B5A5        .000261437908496732
T4        SUBOBJECT_NAME        77        503031        52455354        .012987012987013
T4        OBJECT_ID        3932        C304062D        C30F461B        .000254323499491353
T4        DATA_OBJECT_ID        3664        C304062D        C30F461B        .00027292576419214
T4        OBJECT_TYPE        15        4441544142415345204C494E4B        56494557        .0666666666666667
T4        CREATED        3685        7867081E111F33        78680712111530        .000271370420624152
T4        LAST_DDL_TIME        3575        7867081E11251B        78680712111530        .00027972027972028
T4        TIMESTAMP        3650        323030332D30382D33303A31363A33303A3530        323030342D30372D31383A31363A32303A3437        .000273972602739726
T4        STATUS        2        494E56414C4944        56414C4944        .5
T4        TEMPORARY        2        4E        59        .5
T4        GENERATED        2        4E        59        .5
T4        SECONDARY        2        4E        59        .5
/*
在這個結果中咱們能夠看到,oracle數據庫給t2,t4的全部字段都作了統計信息.
對錶t3的object_id(索引字段)作了統計信息.
由此得出結論,
在指定for all columns 和不指定任何參數的時候oracle會給全部字段作統計信息,在指定for indexed columns時,oracle只給[b]有索引的字段進行字段信息統計[/b],若是咱們別有必要給全部字段統計信息時,這個屬性就頗有用了.
*/

--這裏是對於索引的統計信息
select table_name,index_name,blevel,leaf_blocks,distinct_keys,
        avg_leaf_blocks_per_key avg_leaf_blocks,avg_data_blocks_per_key avg_data_blocks,clustering_factor,num_rows
from user_indexes where table_name in ('T1','T2','T3','T4');
TABLE_NAME        INDEX_NAME        BLEVEL        LEAF_BLOCKS        DISTINCT_KEYS        AVG_LEAF_BLOCKS        AVG_DATA_BLOCKS        CLUSTERING_FACTOR        NUM_ROWS
T1        PK_T1_IDX                                                       
T2        PK_T2_IDX                                                       
T3        PK_T3_IDX                                                       
T4        PK_T4_IDX        1        9        3932        1        1        2143        3932

--從這裏咱們能夠看出,只有表t4有索引統計信息.
--再綜合前面的咱們就會發現,若是在運行analyze table是咱們不指定參數,oracle將收集對於特定表的全部統計信息(表,索引,表字段的統計信息)

補充,truncate命令不修改以上統計信息
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代碼:
truncate table t1;
truncate table t2;
truncate table t3;
truncate table t4;
--咱們在查看錶和索引的統計信息
select table_name,num_rows,blocks,empty_blocks from user_tables where table_name in ('T1','T2','T3','T4');
TABLE_NAME        NUM_ROWS        BLOCKS        EMPTY_BLOCKS
T1        3930        55        1
T2                       
T3                       
T4        3933        55        1

--索引的統計信息
select table_name,index_name,blevel,leaf_blocks,distinct_keys,
        avg_leaf_blocks_per_key avg_leaf_blocks,avg_data_blocks_per_key avg_data_blocks,clustering_factor,num_rows
from user_indexes where table_name in ('T1','T2','T3','T4');
TABLE_NAME        INDEX_NAME        BLEVEL        LEAF_BLOCKS        DISTINCT_KEYS        AVG_LEAF_BLOCKS        AVG_DATA_BLOCKS        CLUSTERING_FACTOR        NUM_ROWS
T1        PK_T1_IDX                                                       
T2        PK_T2_IDX                                                       
T3        PK_T3_IDX                                                       
T4        PK_T4_IDX        1        9        3932        1        1        2143        3932

--咱們再對以上各表作一次分析
analyze table t1 compute statistics for table;
analyze table t2 compute statistics for all columns;
analyze table t3 compute statistics for all indexed columns;
analyze table t4 compute statistics;

--如今再來查看錶和索引的統計信息
select table_name,num_rows,blocks,empty_blocks,initial_extent,'8192' block_size from user_tables where table_name in ('T1','T2','T3','T4');
TABLE_NAME        NUM_ROWS        BLOCKS        EMPTY_BLOCKS        INITIAL_EXTENT        BLOCK_SIZE
T1        0        0        8        65536        8192
T2                                65536        8192
T3                                65536        8192
T4        0        0        8        65536        8192

--索引的統計信息
select table_name,index_name,blevel,leaf_blocks,distinct_keys,
        avg_leaf_blocks_per_key avg_leaf_blocks,avg_data_blocks_per_key avg_data_blocks,clustering_factor,num_rows
from user_indexes where table_name in ('T1','T2','T3','T4');
TABLE_NAME        INDEX_NAME        BLEVEL        LEAF_BLOCKS        DISTINCT_KEYS        AVG_LEAF_BLOCKS        AVG_DATA_BLOCKS        CLUSTERING_FACTOR        NUM_ROWS
T1        PK_T1_IDX                                                       
T2        PK_T2_IDX                                                       
T3        PK_T3_IDX                                                       
T4        PK_T4_IDX        0        0        0        0        0        0        0
--由此得出結論,truncate命令不會修改數據的統計信息,--也就是若是咱們想讓CBO利用合理利用數據的統計信息的時候,須要咱們及時的使用analyze命令或者dbms_stats從新統計數據的統計信息