[英]What is happening when you run the query “SELECT * FROM table_name WHERE column_name;”?
我有一个包含几列的数据库表。 其中一列旨在用作TINYINT（1）DEFAULT 0的布尔设置。
我不小心发现，如果您运行此查询
SELECT * FROM table_name WHERE column_name;
它返回column_name = 1的行。
我很好奇知道MySql用于处理此查询的逻辑。
正如文档在“选择语法”中所述（（ http://dev.mysql.com/doc/refman/5.1/en/select.html ）
where_condition是一个表达式，对于要选择的每一行，其值为true
因此，将简单列名评估为布尔值，并选择相应的行。 您会发现它也适用于int。
Select * from table_name where column_nameِ = 'value'
[英]Select * from table_name where column_nameِ = 'value'
SELECT * FROM table_name WHERE column_name like％value％IN（SELECT…？
[英]SELECT * FROM table_name WHERE column_name like %value% IN (SELECT …?
MYSQL：WHERE NOT LIKE'％（SELECT column_name FROM table_name）％'
[英]MYSQL: WHERE NOT LIKE '%(SELECT column_name FROM table_name)%'
SELECT column_name FROM（选择TABLE_NAME FROM TABLE_OF_TABLES）
[英]SELECT column_name FROM (SELECT table_name FROM TABLE_OF_TABLES)
我需要从tbl1查询此select column_name，其中remarks ='accepted'以及与另一个表的union查询
[英]I need a query for this select column_name from tbl1 where remarks = 'accepted' together with a union query with another table
是否有可能在SQL中SELECT * FROM表WHERE列1 =某些东西而不是column_name = something
[英]Is it possible in SQL to SELECT * FROM a table WHERE the column 1 = something and not the column_name = something
我怎么能 SELECT FROM sqlite3_table WHERE column_name IN variable tuple？
[英]how can i SELECT FROM sqlite3_table WHERE column_name IN variable tuple?
选择列 FROM table_name WHERE username=$_SESSION['username'] 不起作用
[英]Select column FROM table_name WHERE username=$_SESSION['username'] not working
无论查询中的 where 子句如何，如何从表中获取 max(column_name)？
[英]How to get max(column_name) from a table irrespective of a where clause in the query?
声明:本站的技术帖子网页，遵循CC BY-SA 4.0协议，如果您需要转载，请注明本站网址或者原文地址。任何问题请咨询:yoyou2525@163.com.