SQL > SQL????? > Count

? ????? COUNT ? ???? ???? ??????. ???? ???? ??? ??? ??? ???? ?????. (COUNT) ? ???? ??? ????? ??? ???? ??????? ???? ?? ???. ? ???;

SELECT COUNT("???")
FROM "???";

?? ?? ??? ??? ??? store_name ?? ?? ??? ??? ???? ??,

Store_Information ??
Store_NameSalesTxn_Date
Los Angeles150005-Jan-1999
San Diego25007-Jan-1999
Los Angeles30008-Jan-1999
Boston70008-Jan-1999

??? ?????,

SELECT COUNT (Store_Name)
FROM Store_Information
WHERE Store_Name IS NOT NULL;

??:

COUNT (Store_Name)
4

"IS NOT NULL" ? "? ??? ??? ????" ? ????.

COUNT ? DISTINCT ? ?? ?? ???? ??? ??? ???? ??? ???(? ???? ????? ???? ????)? ???? ?????. ?? ?? ???? ??? Store_Name ? ?? ??? ?? ?? ??? ?????,

SELECT COUNT (DISTINCT Store_Name)
FROM Store_Information;

??:

COUNT (DISTINCT Store_Name)
3

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