问题
I saw one or two threads talking globally about case sensitivity, but my question is more specific.
I understand the interest of case insensitive searches on text values for example.
But why would we use case-insensitive database names, tables and columns?
Isn't it going to lead to mistakes? Script languages that use databases are all case-sensitive, so for example if we didn't use the right case for a field it will not be found...
回答1:
The SQL:2008 and SQL-99 standards define databases to be case-insensitive for identifiers unless they are quoted. I've found most ORMs will quote identifiers in the SQL they generate.
However, as you probably know not all relational databases strictly adhere to the standards. DB2 and Oracle are 100% compliant. PostgreSQL is mostly compliant, except for the fact that it automatically lowercases anything that isn't quoted (which personally I prefer.)
mySQL gets a bit weird, since it stores each table as a file on the file system. For this reason, it's subject to the case sensitivity of the file system. On Windows:
CREATE TABLE FOO (a INTEGER);
CREATE TABLE 'Foo' (a INTEGER); -- Errors out, already exists
Where-as on Linux:
CREATE TABLE FOO (a INTEGER); -- Creates FOO table
CREATE TABLE 'Foo' (a INTEGER); -- Creates Foo table
SQL Server is even stranger. It will preserve the case on creation, however let you refer to it in any way after (even if you quote the name!) You can't create two tables whose only difference is their casing. Note: SQL Server does have configuration options that control this stuff though, as case-sensitivity of identifiers will depend on the default collation of the database instance. How confusing!
While for the most part I agree with you that computers (programming languages, databases, file systems, URLs, passwords, etc) should be case-sensitive, all systems are implemented independently and may or may not adhere to standards that may or may not exist. Implementing a case-senstive database is definitely possible, if you know the ins and outs of your particular database system and how it behaves.
It's really your responsibility to implement your system in a way that works for you, and not the entire technology industry to implement everything in a consistent way to make your life easier.
回答2:
The main advantage of using case sensitivity is that when we deploy it on the client site, our DB works regardless whether the client's SQL Server is set up case sensitive or not, so yes it really isn't a good idea and I don't know why anyone would use case-insensitve database tables/columns.
回答3:
If you would redo all the it industry today, with the knowledge and technology you might default to do everything case sensitive with the only exception of things especially asked for being not case sensitive.
But back in the days before I was born and even when I started working (ok, playing) with computers many computers couldn't even differentiate between upper and lower case letters. I build a might complicated card to plug into my fake apple II to make it understand the difference.
So I guess in these days having something like a difference between upper and lower case was something like having a retina display nowadays. Its cool if you have it. And in 10 years we might ask why anybody ever created an application without such displays in mind, but today it just isn't that relevant.
Same is true for databases (and file systems) since many of them and their respective standards go back to the 70s at least.
来源：https://stackoverflow.com/questions/12076995/databases-why-case-insensitive