SQL statement count vs. GROUP by

1. Multi-line function

which

Max (field)-----------Maximum value

Min (field)----------Minimum value

sum (field)-----------sum

AVG (field)-------------averaging

Cont (field or *)----------count the field data, * Calculate the number of rows of data

Several are multi-line functions, if there is such a function in the statement without writing groupby a field

The function avg () calculates all the rows of data and gets a single data, which is a multiline function, and if you have a function in your statement, such as AVG (), and you do not write a group by a field, then the function avg () calculates all rows of data to get a result.

SQL statement count vs. GROUP by