Use Sql Count to count the number of rows of a table.
The above statement counts non NULL value of the column_name
That could cause some confusion if you happened to have NULL values in the column_name as the total does not match the total number of rows. If you are interested in counting the number of records regardless of the values, use COUNT(*) instead.
The Sql syntax:
That differences can also be useful when you want to find out if there is any NULL value in a certain field. So,simply compare the two results, when the total is different then you know there is Null value in that column. You can put the two COUNT keywords both in the Select statement, as follows:
There is also a time when you only want to know the COUNT of unique values of a field. To do this you need to add DISTINCT keyword into the Sql Count. Different with Sql Distinct with which you list the values, here you only get the count.
Use the CONTACTS table once again.
You are going to implement the COUNT.
|1||White||Alan||210 George St||Sydney||NSW||2000|
|2||Johnson||Benjamin||11 Cooper St||Surry Hill||NSW||2010|
|3||Brown||Peter||72 Haymarket St||Haymarket||NSW||2000|
|4||Anderson||Thomas||33 Collins St||Melbourne||VIC||3000|
|5||Gomdas||Tony||78 Marine Pde||Coolangatta||QLD||4225|
The result would have been the same if you use COUNT(*), because there is no NULL value in State field.
The core of Sql, selecting data from table.
Conditionally selecting rows from table.
Eliminating duplicate values in the output.
Getting the sum of a field
This function will return the highest value.
This function will return the lowest value.
This function will return the average value.
Sql Order By
Sorting the output
Sql And Or
Connecting two or more conditions in the Where or Having clause.
Sql Group By
Grouping rows into sets.
To filter the result of aggregation
Pattern searching for conditions in Where or Having clause
Added to conditions to show results between two values.
Return from Sql Count to Sql Commands
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