by index

Key operationKeys * shows all the keysKeys key* Show all keys with keyexists name to determine if the key with name, the successful return 1, the unsuccessful return 0Del Key1 Delete Key1Expire Key1 100 sets an expiration time of 100 seconds for Key1

The function is to not standardize the address, for example: Beijing Haidian District West two flag xx hospital xx number; Shijiazhuang Qiaoxi District xx road xx; cleaning is the structured address data for the canonical provinces, cities, and

One, how to view the execution plan of SQL statement1, in the Sql*plus environmentPerform set AUTOTRACE on to turn on startup auto-tracking, as follows (the red font below is the typed command):chenzw>set Autotrace onChenzw>select * from EMP;    

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If we want to optimize the database, we can use the following five methods to optimize the database system: If we want to optimize the database, we can use the following five methods to optimize the database system: 1.1.1 Summary If we want to

Continue to look at the second case of the query, including the table connection: SQL> Create Table T as select * From dba_users; The table has been created. SQL> Create Table T1 as select * From dba_source; The table has been created. SQL>

The original statement is as follows: Select sum (sl0000) from xstfxps2 whereDhao00 in (Select dhao00 from xstfxps1 where trunc (ywrq00) = trunc (sysdate)And khdm00 = '000000 ');Time in use: 00: 02: 49.04Execution Plan-----------------------------

RULE-based optimizer (learning notes) and rule learning notesCui Hua's Oracle-based SQL optimization learning notes1.1 RULE-based Optimizer (1) CBO (2) RBO Compared with CBO, RBO has obvious permissions. When RBO is used, once a problem occurs in

1. Data type1 first, basic use 2 1. Use 3 2. Definition method 4 3. Common operation + built-in method 5 c12> Ii. Summary of the type of change 6 1. Save a value or save multiple values 7 2. You can have multiple values, and what type of value

In the view of union all, if you are using the traditional rownum paging method, such asWHERE RowNum WHERE LineNum >=nBecause when Oracle executes to LineNum >=n, it will be overwhelmed, causing the execution plan to mess up. For example, suppose

You are often confused about the invisible indexes of Oracle 11 GB. Is the index really helpful for user queries? It may be helpful for one query, but it may affect 10 other queries. The index will certainly have a negative impact on the INSERT

The original statement is as follows:Select sum (sl0000) from xstfxps2 whereDhao00 in (Select dhao00 from xstfxps1 where trunc (ywrq00) = trunc (sysdate)And khdm00 = '000000 ');Time in use: 00: 02: 49.04　　 Execution Plan------------------------------

Applicable scenarios Imagine the following SQL Select * FromBD_INVMANDOC_bak t Where t. negallowed is null Or t. negallowed = 'n' If the negallowed column has only two values: Y and N, and NULL exists Therefore, when we create an index in the

In the view of Union all, if the traditional rownum paging method is used, for exampleWhere rownum Where linenum> = NBecause Oracle will be overwhelmed when it runs to linenum> = N, leading to execution plan disorder. For example, assume that

SQL> select ID from (select/* + index (SI sie_invoices_n3) */Si. ID from binbin1 Si,2 binbin2 BS where Si. ID = BS. ID and Si. type = 'ar _ invoice' and3 Si. import_failed_reason is null and (Si. imp_1__mis_flag is null or Si. imp_1__mis_flag = 'n')

Example 1:If LARGE_TABLE is a large table with no index on the username column, run the following statement:SQL> SELECT * FROM LARGE_TABLE where USERNAME = 'test ';Query Plan-----------------------------------------Select statement Optimizer =

In pinwu performance optimization, Chapter 4.4.3 describes the two features of composite indexes: prefix and optionality. What is prefix? The book explains how to exclude skip scan index (there are not many pre-index columns, such as gender). If the

(Hdu step 3.2.3) Super Jumping! Jumping! Jumping! (DP: Calculate the largest sum of the longest ascending subsequence)     Question:   Super Jumping! Jumping! Jumping! Time Limit: 2000/1000 MS (Java/Others) Memory Limit: 65536/32768

B-Tree indexes are superior to BitMap indexes. 1. Experiment description: Operating System: rhel 5.4x86 Database: Oracle 11g R2 Lab Description: This experiment aims to demonstrate that the B-Tree index performance is superior to the BitMap

Pandas data structures and indexes are Getting Started Pandas must learn the content, here in detail to explain to you, read this article, I believe you Pandas There is a clear understanding of data structures and indexes. first, the data structure