In the previous query needs to be "accurate" to shut down the query, "complete" the full input in order to check the appropriate result, But in the actual development process will usually require the user may not know the "exact", "complete" keyword, Then you need to provide a less stringent forms of inquiry, namely fuzzy query, just type part can be done about the inquiry. First, fuzzy query 1 , using the keyword LIKE Syntax: the SELECT < field list | *> the FROM table [ the WHERE field names LIKE% keyword% ] ; Description: Wildcard _ (0-1 represents any character), % (0 represents any of a plurality of characters) 举例：SELECT * FROM tb_student WHERE student_name LIKE '%娘%' OR phone LIKE '%娘%' OR address LIKE '%娘%' OR email LIKE '%娘%'; 2、使用BETWEEN END关键字 Syntax: the SELECT < field list | *> the FROM table [ the WHERE field name AND BETWEEN start value end value ] ; Description: "start value" and "end value" are included 举例：SELECT * FROM tb_score WHERE student_score >=80 AND student_score <= 90; SELECT * FROM tb_score WHERE student_score BETWEEN 80 AND 90; 3 , using the IN keyword Syntax: the SELECT < Field List | *> the FROM table [ the WHERE <field name IN (a list of possible values)> ] ; Note: If the query contains the keyword IN at the back of the "possible values list", considered to be legitimate Example: - Query "java" and "HTML" Course information the SELECT * the FROM tb_subject the WHERE SUBJECT_NAME = "java" OR SUBJECT_NAME = "HTML"; the SELECT * the FROM tb_subject the WHERE SUBJECT_NAME the IN ( "java", "HTML"); . 4 , using regular expressions (REGEXP) clause Syntax ,: 1 the SELECT < field list | *> the FROM table [ the WHERE <field name REGEXP regular expression rules> ] ; Syntax ,: 2 the SELECT < matched value > REGEXP, < regular expression rules > ; Explanation: The value is matched regular expression rules if the meet, which matches the success of the display 1, 0 otherwise 举例：SELECT * FROM tb_student WHERE email REGEXP '^([a-zA-Z0-9]+)*@([a-zA-Z0-9]+)\.([a-zA-Z]{2,5})$'; -- ^[\u2E80-\u9FFF]+$ SELECT * FROM tb_student WHERE not student_name REGEXP "^([u0391-uFFE5]{2,4})$"; Second, aggregate functions . 1 , COUNT (): number of statistics records satisfying the condition 2 , the SUM (): summation . 3 , the AVG (): calculating an average value . 4 , MAX (): selecting the maximum value . 5 , MIN (): for the minimum The SELECT * the FROM tb_score LIMIT 10 , 5 ; - for tb_score table, each page displays up to five records, please check the second page of the SELECT * the FROM tb_score LIMIT 5 , 5 ; the SELECT SUM (student_score) the FROM tb_score; the SELECT AVG (student_score) the FROM tb_score; the SELECT MAX (student_score) the FROM tb_score; the SELECT MIN (student_score) the FROM tb_score; pageCount = (rowCount%pageSize == 0) ? rwoCount / pageSize : rowCount / pageSize + 1; Three, mysql commonly used functions: 1 , the character-related functions: the SELECT CONCAT (student_no, ' ---- ' , student_name) the FROM tb_student; the SELECT address, the LENGTH (address) the length of the FROM tb_student; the SELECT the UPPER ( "afaag"); the SELECT the LOWER ( "asdKKJF" ); 2 , values related functions: - the ROUND (X-, D) rounding the SELECT the ROUND ( 85.65622 , 2 ); - the ROUND (X-) rounded, d is 0 the SELECT the ROUND ( 85.65622 ); -`TRUNCATE` (X, D) function truncates the SELECT TRUNCATE ( 85.65622 , 2 ); - ` MOD` (N, M) modulo the SELECT the MOD ( 10 , . 3 ); . 3 , the date-related functions: Date function calculates the time difference TIMESTAMPDIFF(unit,datetime_expr1,datetime_expr2); Description: unit: Pointing to calculate what type of difference datetime_expr1: subtrahend datetime_expr2: minuend