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Either count (*) or COUNT (1) or count ([column]) in SQL Server is perhaps the most commonly used aggregate function. Many people actually distinguish between the three. This article will explain the role of these three, relations and the underlying principles. I often see some so-called optimization recommendations that use

Odd sum (1), sum (2), count (1), count (6), count (*) in SQL: Total number of statistics, sumcountSQL statistical functions The SQL statistical function has count statistics, and uses sum to accumulate the specified field value with sum, but note that sum (1) is special.Sum (1) is equivalent to

Summary of differences between count (*), count (1), and count (col) in MySQL, mysqlcol Preface The count function is a function used to count records in tables or arrays. count (*) returns the number of rows to be retrieved, whet

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 true that I remember wrong, it is evident that the code review how usefu

Oracle Count Millions paging query total number of records, total bar count optimizationOracle Count millions query total number of records, total bar count optimizationRecently do a project, do paging, found that paging query speed is very slow, paging I do is two queries, one is the total number of queries, one is to

Difference between count (*) and count (1) and count (column name)Execution result:Count (*) includes all columns, equivalent to the number of rows. During the statistical result, the column value is not ignored as null.Count (1) includes ignoring all columns, represented by 1CodeRow. The column value is null.Count (column name) only includes the column name. Dur

Analysis of the differences between count (1) count (*) count (col) and performance count (1) and count ), in addition, the count (col) statistics for all rows are performed for records whose col columns are not empty. If an index

Count the word count of historical records and the word count of historical records I haven't studied for a long time. I suddenly want to read the history to improve my strength. Then, I downloaded the full text of historical records online.I don't know if it is a complete set, so I had a whimsy and wanted to count the

There is no difference between count (1) and count (*) (Execution Plan and statistics), and both are statistics.AllLineCount (COL) Counts records whose Col columns are not empty. If an index exists, indexes can be used no matter whether or not Col is empty.Test HR @ orcl> select count (1) from t; Execution Plan -------------------------------------------------

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 statisticsLineCount (col) Statistics c

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> set autotrace on;Sql> Select A.document_id,count (*) from table_name

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 if your table has only on

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 primary key (the Union primary key) is also faster than

This article brings you the content of MySQL large table in the use of count () and MySQL count () of the optimization, there is a certain reference value, the need for friends can refer to, I hope to help you. A single table contains 6000w+ data, but you can't split it. How much data is needed in the separate tables, how many of a products there are, and how many of these data are available for B products

COUNT (*) is typically an index scan of a primary key, and Count (column) does not necessarily COUNT (*) is the total number of records in the statistics table, count (column) is the number of records for all eligible columns in the tables Count, if there is no where lim

[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 array as the judgment condition for loop end, in PHP, [PHP source code re