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SQL COUNT () function tutorial
The count () function returns the number of rows that conform to the specified criteria.Database count (column_name) syntaxThe specified column for the quantity value returned by the COUNT (column_name) function (the null value will not be
Orderprice values above the Orderprice averageSelect Customerfrom orderswhere orderprice> (select AVG (orderprice) from Orders)The results are as follows
Customer
Bush
Carter
Adams
SQL COUNTThe count () function returns the number of rows that match the specified condition (Null does not
Label:SQL Server Databasethe Count () function returns the number of rows that match the specified criteria. The syntax SQL count (column_name) syntax count (column_name) function returns the number of values for the specified column (NULL does not
),COUNT (DISTINCT COL3),COUNT (COL4),COUNT (DISTINCT COL4)From TBRun the Select one by one to see the execution plan, and you'll see that the first five execution plans look the same, all inx_tb_col3, because the system determines that the index size of the COL3 is less than
Check whether the SQL server has repeated values. Check whether the SQL server has repeated values.A string is "1; 2; 1; 1; 1 ".Excuse me:How to implement the following functions in SQL SERVER:1. check whether there are repeated numbers in the string.If a number already exists, an error message is returned.If no duplic
(field name) Also note that if the field values are duplicated, the number of records will be counted repeatedly, if you need to count the number of different values, you need to use Count (distinct field name), for example, suppose there is a person table PP, There is a fi
The count Statement supports *, column name, constant, and variable, and can be modified with the distinct keyword, and count (column name) does not accumulate null records. Here are some examples to demonstrate the count rule: for example, to make statistics for the following table, all columns are represented by the
The Count Statement supports *, column name, constant, and variable, and can be modified with the distinct keyword, and count (column name) does not accumulate null records. Here are some examples to demonstrate the Count rule: for example, to make statistics for the following table, all columns are represented by the
First of all, let's look at one of the steps here that translates into banner, which requires pivot, step-by-step Then look at the overall query results for the two query methods after the main table join So take a look at the latter query method is also through the industry after the conversion to do the join execution plan, you can see only the Word table for a search (this is the index seek, but the temporary throw-off index) Looking at two SQL
ON SC.[C#]=C.[C#] GROUP BY [S#] HAVING COUNT(*)=COUNT(DISTINCT [S#]))
5. query the number of students who have selected the course
-- Implementation code:
SELECT students = COUNT (DISTINCT [S #]) FROM SC
6. query the student ID and organization of more than 5 Electiv
1. Select year (ordertime) annual, sum total sales from order form group by year (Ordertime) 2, monthly select years (Ordertime), Month ( ordertime) month, sum (total) Sales totals from order form GROUP by year (Ordertime), Month (Ordertime 3, daily Select year (ordertime), Month ( ordertime) month, day (ordertime), sum (total) Sales totals from order form GROUP by year (Ordertime), month (Ordertime), Day (Ordertime) Also daily can be this: select CONVERT (char (8), ordertime,112) dt,sum (total)
Label: 1.
Select Year (ordertime) annual,
sum total sales from
order Form GROUP by year
(Ordertime)
2, monthly
Select Year (ordertime), Month
(ordertime) months,
sum (total) sales totals from
order Form
Group by year (Ordertime),
month (Ordertime
3, daily
Select year (ordertime), Month
(ordertime),
Day (ordertime),
sum (total The sales total from
order Form
Group by year (Ordertime),
month (ordertime),
Day (ordertime)
can also be done in addition daily:
Select CONVERT (char (8), ordertime,112
As mentioned on the previous page,COUNT is one of the functions. Because of its wide use, we have made a special offer here to discuss it. Basically,Count allows us to count how many of the data in the table is selected. Its syntax is:Select COUNT ("Field name")From "table name";For example, if we want to find out how
T_ SQLInCountFunction
CountFunction Definition visibleMsdn. Definition:Count ({[[All | distinct] expression] | *})
SoCountThere are two ways to useCount (expression)AndCount (*)Returns the value of a column for a table.
1.Count (*)The number of rows in the returned table. It does not filterNullAnd duplicate rows.
2.Count (expression)Will filter outNullV
Tags: style blog http color using AR strong data SP1, AnnualSelect Year(Ordertime) years,sum(total) Sales totals fromOrder FormGroup by Year(ordertime)2, monthlySelect Year(Ordertime) years,Month(ordertime) month,sum(total) Sales totals fromOrder FormGroup by Year(ordertime),Month(Ordertime3, DailySelect Year(Ordertime) years,Month(ordertime) month, Day(Ordertime) Day,sum(total) Sales totals fromOrder FormGroup by Year(ordertime),Month(ordertime), Day(Ordertime) In addition also daily c
records in the table have filtered out the records whose category is 3, which are not included in group processing.
Supplement: complete execution sequence of SQL select statements
The complete execution sequence of the SQL SELECT statement:1. The from clause assembles data from different data sources;2. The WHERE clause filters records based on specified conditions;3. The group by clause divides da
also be extended to handle unknown. The result of And:true and unknown is unknown,false and unknown result is false,unknown and unknown result is unknown. The result of Or:true or unknown is true,false and unknown result is unknown,unknown and unknown result is unknown. The result of not:not unknown is unknown. * If the WHERE clause predicate evaluates to a tuple false or unknown, then the tuple is not written to the result set. SQL uses the special
$ Cid $ _ GET [id];
$cid = $_GET['id']; Reply content: divide by 10 and use group by and count aggregate again. Let's make SQL into a dynamic language. It's really true-I'm a cainiao and can write it at will ···
DECLARE @ grade TABLE (
[Id] [int] IDENTITY (1, 1) not null,
[CId] [int] not null,
[SId] [int] not null,
[Sgrade] [int] NOT NULL
);
Insert into @ grade (cId, sId, sgrade)
Reply content:Divided by 10 after the group by count once again aggregate up and quickly make SQL dynamic language it, really-I am a rookie, write and write ...
DECLARE @grade TABLE (
[ID] [int] IDENTITY (*) Not NULL,
[CID] [int] not NULL,
[SId] [INT] Not NULL,
[Sgrade] [INT] Not NULL
);
INSERT into @grade (cid,sid,sgrade) VALUES (1,0,0);
INSERT into @grade (cid
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