Linux SQL statement concise tutorial --- COUNT, concise tutorial --- count

Linux SQL statement concise tutorial --- COUNT, concise tutorial --- count

As mentioned on the previous page,COUNTIs one of the functions. It is widely used and we will discuss it here. Basically,COUNTThis allows us to count how many pieces of data are selected in the table. Its syntax is:

Select count ("column name ")
FROM "table name ";

For example, if we want to find out which of the following store_name columns in our example table are not blank,

Store_InformationTable

Store_Name	Sales	Txn_Date
Los Angeles	1500	05-Jan 1999
San Diego	250	07-Jan-1999
Los Angeles	300	08-Jan 1999
Boston	700	08-Jan 1999

Let's get,

Select count (Store_Name)
FROM Store_Information
WHERE Store_Name is not null;

Result:

COUNT (Store_Name)

4

"Is not null" means "this field is not blank.

COUNTAndDISTINCTIt is often used together to find out how many different pieces of data are in the table (as for what the data is actually not important ). For example, if we want to find out how many different store_names exist in our table, we will enter,

Select count (DISTINCT Store_Name)
FROM Store_Information;

Result:

COUNT (DISTINCT Store_Name)

3

Linux test results:

Reprinted, please note: Xiao Liu