Derby数据库表列名称格式在查询中不一致 [英] Derby Database Table Column Name Format Inconsistent in Query
问题描述
查询Derby数据库时，我发现对于一些表，我必须双引号列名称并使用表名来限定列名，但是对于一些其他表，我不需要。这些表会发生什么，如何使所有表相同，并且可以查询它们，而不需要双引号和表名限定符？我使用NetBeans IDE的Sql Command工具。以下是这些不同的查询。
When query a Derby database, I find out that for some tables I have to double quote the column name and use table name to qualify the column name, but for some other tables I don’t need to. What happens to these tables and how can I make all tables the same and can query them without the double quote and the table name qualifier? I am using NetBeans IDE’s Sql Command tool. Below are those different queries.
Set schema app;
Select * from table1 where table1."state" = ‘CA’;
Select * from table2 where state = ‘CA’;
推荐答案
将tablename或列名称放在引号中通过术语分隔标识符执行两项操作：
Putting a tablename or column name in quotes, sometimes referred to by the jargon-y term "delimited identifiers" does two things:
- 允许您使用否则为保留关键字的单词命名列WHERE或SELECT）
- 指示数据库系统使用敏感规则处理名称，而不是不区分大小写规则
- Allows you to use words that are otherwise reserved keywords (e.g., naming a column "WHERE" or "SELECT")
- Instructs the database system to process the name using case sensitive rules, rather than case-insensitive rules
因此，如果您最初使用CREATE TABLE语句创建table3，并在双引号中指定table3这个，那么你永远都要用双引号引用它的名字。
So if you originally created "table3" with a CREATE TABLE statement that specified "table3" in double quotes like this, then you will forever after have to refer to it with the name in double quotes.
select * from table3
由数据库处理，如同
select * from TABLE3
while
select * fromtable3
将成功匹配您创建的表创建表table3
will successfully match the table you created as create table "table3"
href =http://db.apache.org/derby/docs/10.9/ref/crefsqlj34834.html =nofollow> http://db.apache.org/derby/docs/10.9/ref/crefsqlj34834 .html
See: http://db.apache.org/derby/docs/10.9/ref/crefsqlj34834.html
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