PHP learning notes: MySQL database operations, learning notes mysql

PHP learning notes: MySQL database operations, learning notes mysql

Update statement

Update table name set field 1 = value 1, Field 2 = value 2 where Condition

Exercise:

Set the password of the person with the username '小' to 123456 @

Statement: UPDATE crm_user SET userpwd = '2017 @ 'where username LIKE '% ';

Effect

Group by and having: Group query having Group query Conditions

Syntax: select a, COUNT (B) from table group by a having count (B)> 2

MysqlBuilt-in statistical functions

Count (column name) Total

Sum (column name) summation

Avg (column name) Average

Max (column name) Maximum Value

Min (column name) Minimum value

Example:

1. Calculate the average number of classes

SELECT class, scores, AVG (scores) FROM jian_scores group by class;

2. Calculate the average score of the class, and the score must be higher than 70

SELECT class, scores, AVG (scores) FROM jian_scores group by class having avg (scores)> 70;