After checking the manual, we can find that the SQL _CALC_FOUND_ROWS keyword is used to count the total number of results that meet the filtering conditions (not limited by Limit, if you are interested, you can learn the MYSQL Keyword: SQL
The convenient way to count the total number of rows in the query result in MYSQL saves the keyword count (*) bitsCN. comMYSQL:
After checking the manual, we found that this keyword is used to count the total number of results
The number of records in the database table is:
Sql> Select COUNT (*) from table_name t;
1, using the statistical results of COUNT (*):
Sql> alter session Set Nls_language = "American";
Sql> set timing on;Sql>
Let's take a look at the description of Count (*) and Count (col) in Bol:COUNT(*Returns the number of items in the group. IncludingNULLvalues and duplicates. COUNT( Allexpression) evaluates expression for each row in the group and returns the number
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
Difference between Select count (*) and Count (1) in SQL server and the execution Method
In SQL Server, Count (*), Count (1), or Count ([column]) is perhaps the most common aggregate function. Many people cannot tell the difference between the three.
The difference between Select count (*) and Count (1) in SQL server and the execution method, selectcount
In SQL Server, Count (*), Count (1), or Count ([column]) is perhaps the most common aggregate function. Many people cannot tell the difference
Mysql -- SQL Optimization-count the number of Certain types and the number of mysqlsql Optimizations
Sometimes we want to count the number of such SQL statements. In addition to full table scanning, filesort takes 1.34 seconds.
In SQL Server, COUNT (*) or COUNT (1) or count ([column]) may be the most commonly used aggregate function. A lot of people actually have a clear distinction between the three. This article will describe the roles, relationships, and principles
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
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