count time difference

1. The difference between count (1), COUNT (*), and count (column name)Believe that you are always at work, or in the study of Count () in the end how to use faster. There has been a lot of doubt, some people say that count (*) faster, some people

Execution effect: 1. Count (1) and COUNT (*) when the table has a larger amount of data, using count (1) is more time-consuming than using count (*) when analyzing the table. From the execution plan, the effect of count (1) and COUNT (*) is 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>

AIn general, select COUNT (*) and select COUNT (1) both return the same resultIf the table does not have a primary key (Primary key), then count (1) is faster than COUNT (*),If there is a primary key, the primary key is the fastest when the

What are you looking for, and you have a container or you have a range divided by the iterator-everything you are looking for is in it. How do you complete the search? The arrow in your arrow bag has thisCount, count_if, find, find_if, binary_search,

The number of records in the database table is as follows: SQL> select count (*) from table_name t; COUNT (*)----------6873 1. Statistical results using count: SQL> alter session set nls_language = "American "; Session altered. SQL> set timing

Tested under MySQL 5.6.MyISAM Engine:When creating a data table, MySQL generates 3 files, respectively (table: Test):TEST.FRM, Test. MYD, Test. Myi file,TEST.FRM is the table structure, Test.myd is the file that holds the data, Test.myi is the file

Simple analysis of the difference and performance of Count (1) count (*) count (COL) url:http://blog.csdn.net/dba_waterbin/article/details/8569257 count (1) and COUNT (*) have no distinction (execution plan and statistics), and are all

I previously added a field to this list to help me prompt the administrator if the product list has a Status field such as modification, so I can conclude that this field is added.First, let's take a look at how I previously wrote this prompt Status

Today, when modifying the management List of background users, we found the list loading slow bug! Tens of seconds! Data is a little more than other lists, but there are more than 4000 records. It was good before. Why is it so slow? Today, when