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SQL> select rowid from;Rowid------------------Aaaq/laacaaabacaaaAaaq/laacaaabacaabSQL> DESC;Name null? Type-----------------------------------------------------------------------------Id not null number (5)NAME VARCHAR2 (35)CREATE_TIME DATESQL> select index_name from user_indexes where table_name = 'a ';INDEX_NAME--------------------------------------------------------------------------------IDX_A_IDSQL> Delete from;2 rows deleted.SQL> commit;Commit c

ROWID determines Based on the index:SQL> select rowid from; ROWID ------------------ AAAQ/LAACAAABacAAA AAAQ/LAACAAABacAAB SQL> desc; Name Null? Type ----------------------------------------------------------------------------- Id not null number (5) NAME VARCHAR2 (35) CREATE_TIME DATE SQL> select index_name from user_indexes where table_name = 'a '; INDEX_NAME ----------------------------------------------

-000c2952edc5| 8 | 08:31:18| 10 | 08:31:40| 12 | 97621dc2-e722-11e5-a858-000c2952edc5| 14 | aaaq| 16 | aaaq| 18 | 13+ ---- + ------------------------------------- Run the following SQL statement on server:Insert test1 select * from test where id> = 10 Although mysql has a warning:Unsafe statement written to the binary logUsing statement format since BINLOG_FORMAT = STATEMENT. However, I can see that serv

ROWID determines the index. When NOTNULL and the data bit is 0, the index block is 0, and the table is at least 1. Then the index cost is 0, and the CBO will certainly select cost. ROWID determines the index. If the index block is 0 when not null and the data bit is 0, and the table is at least 1, the index cost is 0, and the CBO will certainly select cost. ROWID determines Based on the index: SQL> select rowid from;ROWID------------------AAAQ/LA

Query the number of letters in a string (two implementation methods: 1. list and set 2. map set) Question: The number of times a letter appears in a string. For example: String: "abcde % ^ kka27qoq", output format: a (2) B (1) k (2 )... The first method (used in combination with set and list ): Package itheima; import java. util. arrayList; import java. util. linkedHashSet; import java. util. list; import java. util. set ;/***. the number of times a letter appears in a string. For example: Stri

can use the index, it will not be used. The fourth type, when querying the small standard, in the initialization parameters there is aDb_file_multiblock_read_count, this parameter specifies the number of blocks per read, but if you find that the table currently being queried is less than the value of the parameter, the optimizer selects the full table scan.ii. Several common index scan types for SQL statementsFirst, there is a concept that, in addition to getting the value of the index itself,

[Dictionary download] Excellent 4.3 (five strokes) for little penguin input method and small input method-general Linux technology-Linux technology and application information, the following is a detailed description. This is a five-stroke dictionary. Extracted from the pole 7.0 Preview (second edition), in order to further meet the usage habits, special characters in Fcitx are combined into this dictionary, in addition, the automatic screen-on-screen function without duplicate codes (small inpu

. Record the previous image information to the Undo block, modify the data block, and change the modified data block to a dirty state. In addition, the CR block of the data block to be modified is created in the high-speed buffer.7. Execute commit and allocate SCN to the transaction. commit information is stored in the redo buffer.8. The transaction table of the rollback segment header stores information that has been successfully submitted and ends possession of all resources including the TX l

, only with the above symbol (Also note:rownum cannot be prefixed with the name of any base table. (1) Take the first five recordsSELECT * from emp where rownum (2) Remove all records from the first five records.SELECT * FROM (select EMP. *,rownum no from EMP) where no > 5;(3) ranking (by Sal in each department)Select E.*,rownum No from (SELECT * from emp where deptno= ' ORDER by NVL (sal,0)) E UNION ALLSelect E.*,rownum No from (SELECT * from emp where deptno= ' "ORDER by NVL (sal,0))" E UNION