-- If 0 is specified, the current database is used. The statistics are updated before use.
DBCC updateusage (0)
-- Or
DBCC updateusage ('db ')
-- DBCC updateusage correct the rows, used, reserved, and dpages columns of the sysindexes table and the
Use BINARY_CHECKSUM to detect changes in the table's rows without USEAdventureWorks2012; GOCREATETABLEmyTable (column1int, column2varchar (256); values (1, test); values (*) frommyTable; GOUPDATEmyTablesetcolumn2
Using BINARY_CHECKSUM to detect
Translator: ye Jinrong (imysql # imysql.com), source: imysql.com, please reprint it. Cause: It is too slow to make count (*) Statistics on the innodb table, so try to see if you can hurry up. Symptom: Let's take a look at several test cases. 1. Test
The table structure is as follows:Mysql> Show CREATE TABLE user\g;*************************** 1. Row *************************** table:usercreate table:create Table ' user ' ( ' id ' int (ten) unsigned not NULL AUTO _increment, ' name '
The table structure is as follows:
The code is as follows
Copy Code
Mysql> Show CREATE TABLE Userg;1. Row ***************************Table:userCreate table:create Table ' user ' (' ID ' int (a) unsigned not NULL
SQL tuning is primarily about reducing the number of consistent gets and physical reads.
COUNT (1) is compared with COUNT (*):
If your datasheet does not have a primary key, then count (1) is faster than COUNT (*)If you have a primary key, the
The number of records in the database table is:
Sql> Select COUNT (*) from table_name t;
COUNT (*)----------6873
1, using the statistical results of COUNT (*):
Sql> alter session Set Nls_language = "American";
Session altered.
Sql> set timing on;Sql>
Count1) with Count (*) Comparison: If your data table does not have a primary key, COUNT (1) than COUNT (*Fast If there is a primary key, then the primary key (the Federated primary key) as the count condition is also more than count (*) to be quick
SQL Optimization-count, table join sequence, conditional order, in, exist, countexist
1. About count
I have read some articles about count (*) and count (Column). Is the efficiency of count (column) higher than that of count?
In fact, I personally
In ABAP, if we want to use code to get the number of records in a database table, the general practice is to use select COUNT.If you are using the Hana database, there is now a new way to achieve the same goal. The Hana database has a system view
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