--5、找出部门10中的经理(MANAGER)和部门20中的普通员工(CLERK)select * from emp where (deptno=10 and job='MANAGER') or (deptno=20 and job='CLERK');select * from emp where deptno in('10') and job in('MANAGER'); --6、找出部门10中既不是经理也不是普通员工,而且工资大于等于2000的员工s...
SQLite SELECT Query Introduction The SELECT statement is used to make a simple query from a database or a complicated query against some criteria. A SELECT statement does not make any changes to the database. A query or SELECT statement is a command which gives instructions to a database to...
子查询:sub query,查询是在某个 查询结果之上进行的(一条select 语句包含了另外一条select 语句)。子查询分类方式有两种,按位置分类和按结果分类。 按位置分类:子查询(select语句)在外部查询(select语句)中出现的位置。 a)、From 子查询。 子查询跟在from 之后。 b)、where 子查询。 子查询出现where条件中。
" # 绑定变量值 variable = 'some_value' cursor = conn.execute(query, (variable,)) # 执行查询并获取结果 results = cursor.fetchall() # 处理结果 for row in results: # 处理每一行数据 print(row) # 关闭数据库连接 conn.close() 在上面的示例中,我们首先连接到SQLite数据库。然后,准备一个...
使用查询缓存:SQLite支持查询缓存,可以通过设置PRAGMA query_only选项来启用查询缓存。启用查询缓存后,SQLite会将查询语句及其结果存储在缓存中,当下次执行相同的查询语句时,直接从缓存中获取结果,避免了重复执行查询的开销。 使用预编译语句:SQLite支持预编译语句,可以将查询语句预先编译成一个准备语句,然后在需要执行...
Steps to reproduce Run query Company.select(:id, :name) see logs and data Expected behavior Select query add LIMIT 11 to each query in sqlite and mysql database but it is not applying on database lavel. I got all record of table but logs...
功能查询数据库里的数据。 语法结果 = sqlite3.SQLSelect(数据库, 数据表[, 字段名[, 条件]]) 参数 参数 数据类型 解释 数据库 字符串 数据库的文件路径 数据表 字符串 要操作的表名 字段名 字符串 可选参数,要查询的字段名,省略默认为获取所有字段 条件 字
query = "SELECT * FROM users WHERE name LIKE '%a%'" cursor.execute(query) rows = cursor.fetchall() #打印结果 for row in rows: print(row) #关闭连接 conn.close() ``` 在上面的例子中,我们创建了一个名为`users`的表,并插入了一些数据。然后我们执行了一个模糊查询语句,使用`LIKE`和`%`关...
Importantly, we cannot just operate on strings and translate the MySQL query into the SQLite query. Some transformations require acting on the SQLite database and executing SELECTs, INSERTs etc. Therefore, the input may be a MySQL query string, but the output should be the query result, not ...
asqueries. A query in itself is just a statement which declares what data we are looking for, where to find it in the database, and optionally, how to transform it before it is returned. It has a specific syntax though, which is what we are going to learn in the following exercises....