Intelligent video 24/25 Club
Four action statement:
1,删 DELETE
DELETE FROM table WHERE condition
2, increasing INSERT
INSERT INTO table (field list) VALUES (value list)
3、改 UPDATE
SET UPDATE Table = Value field, field = value, the WHERE condition ...
4, check SELECT
SELECT * FROM table WHERE condition
Clause:
WHERE condition
WHERE name='blue'
WHERE age>19
WHERE age<=19
WHERE AGE>=19 AND score<60
WHERE cach>100 OR score>10000
Sort ORDER
ORDER BY age ASC/DESC
ASC ascending order (small to large)
DESC DESC (descending)
ORDER BY price DESC
Price descending order
ORDER BY price ASC,scale DESC
Price ascending order, if the price is the same, then sales in descending order
Clustering GROUP - Consolidated same
Counting COUNT, MIN, MAX, AVG, SUM
SELECT class,COUNT(class) FROM student_table GROUP BY class;
Statistics class size
SELECT class,AVG(score) FROM student_table GROUP BY class;
Statistics for each class average
class score
1 54.25
2 98.5
3 56.5
SELECT class,MAX(score),MIN(score) FROM student_table GROUP BY class;
Statistics for each class highest score, lowest score
Score class name ID
. 1. 1 Xiaoming 34 is
2 2 red 98
. 3. 1 Xiaogang 26 is
. 4 2 Xiaohua 99
. 5 for 3 strong 18 is
. 6 four 3 hours 95
. 7. 1 Liu 57 is
. 8 florets. 1 100
SELECT name,SUM(price) FROM sales_table GROUP BY name ORDER BY SUM(price) DESC;
Query the total consumption of each person, and in descending order
name SUM (price) John Doe 119,000 Zhang 74000 Zhao six 18 is Blue 12 is
LIMIT- limit output, pagination
LIMIT 10; the first 10
LIMIT 5,8; 5 from the beginning to 8
limit (n-1) * 20,20 page n, page 20
Between the clauses are ordered:
WHERE GROUP ORDER LIMIT filtered merge sorting limit
例：SELECT class,COUNT(class) FROM student_table WHERE score>>60 GROUP BY class ORDER BY COUNT(class) DESC LIMIT2;
Database import and export:
TABLE - Right - dump sql file - Select Address
New Database - Right - run sql file