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Author: Cola

Source: Coke’s path to data analysis

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Arithmetic operators calculate fields

Select column arithmetic operator from table;

A new field can be created using the addition, subtraction, multiplication and division operators, or functions that create fields directly after the select command.

To name a newly created field, use the [AS] command

Add +5 to each score column in the SC table to create a new score2 field as follows:

Second, function calculation field

01 Date Function

YEAR(), MONTH() and DAY() are used in the date function to extract all data under a certain date. In the following example, to extract students born on March 3, 2003, you can omit the DATE() function because the sage column is already in the DATE format. Note that the DATE is filtered with single quotes.

In the following example, extract the records of all students born in 2003.

02 Text Function

A function that operates on character data,

【left】 Extract the last name of each student

03 Numerical Functions

A function that processes numeric data. Common ones are:

The result column is rounded

Aggregation function

Functions that summarize numerical data include the following:

The aggregate function yields a single piece of data rather than a series of queries.

01 count function

The Count function counts rows.

–select count(*) from table –select count(DISTINCT columns) from table –select count(DISTINCT columns) from table –select count(DISTINCT columns) from table

Student1 table student1: select * from student1

02 sum function

The Sum function is the Sum over a specified column.

–select sum from table

Sum the results column in the SC table.

Sum over the grades of student number 1:

03 avg function

The Acg function is used to average the columns

Select avg from table

Average the grade column

04 Max function

Returns the maximum value in the specified column.

Select Max from table

Find the highest grade

5 min function

Returns the minimum value in the formulated column.

–select min from table

Find the lowest grade

Comprehensive application of aggregation function

Descriptive statistical analysis