语法-select

connection = mysql.connector.connect(
    host="218.24.35.79",
    user="root",
    password="1qaz2wsx4rfv",
    database="cunchu"
)
# 创建游标
cursor = connection.cursor()
# sql语句
query = "SELECT COUNT(DISTINCT nodes) FROM service"

query = "SELECT nodes FROM service"

cursor.execute(query)

result = cursor.fetchall()

*.关键字：

DISTINCT ：用于在 SQL 查询中去除重复数据的关键字

查询表里多有数据
select * from table_name;
查询表里有多少条数据
select count(*) from table_name;
查询库里有多少条
SELECT SUM(TABLE_ROWS) 
FROM INFORMATION_SCHEMA.TABLES 
WHERE TABLE_SCHEMA = 'cunchu';

　　

 

2.查询特定列的数据 

 3. 条件查询

 4. 函数查询

　　聚合函数如COUNT、SUM、AVG、MIN和MAX可以用于对数据进行汇总计算

 

5. 排序