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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

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>

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

1) count (1) compared to COUNT (*):1. If your data table does not have a primary key, then count (1) is faster than COUNT (*)2, if there is a primary key, then the primary key (Union primary key) as the count of the condition is also faster than

If NULL participates in the aggregation operation, all other aggregation functions except count (*) ignore null. Such as:ID DD1 E2 NULLSelect COUNT (*) from table--the result is 2Select COUNT (DD) from table---result is 1Efficiency issues:When the

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

[PHP source code reading] count function, php source code count function. [PHP source code reading] count function, php source code count function in PHP programming, when traversing the array, it is often necessary to calculate the length of the

[PHP source reading]count function, PHP source Count function In PHP programming, when iterating over an array, it is often necessary to calculate the length of the array as the judgment condition for the end of the loop, and in PHP the operations

In the impression, Count (key) is more efficient than count (*), so the number of rows is counted in the project in Count (field). In the code Reivew was pointed out that the application of count (*), and then checked, and did a simple test, it is

After listening to nearly 20 speeches in the last two days, I felt a lot of harvest, and the deepest feeling was that I still had a long way to go. There are several points to note:Listening to the old cat yesterday, it is a common problem that