SQL Server的Collate语句需要注意

Server: Msg 446, Level 16, State 9, Line 61
Cannot resolve collation conflict for equal to operation.

COLLATE
A clause that can be applied to a database definition or a column 
definition to define the collation, or to a character string expression
to apply a collation cast.
Syntax
COLLATE < collation_name > 
< collation_name > :: = 
    { Windows_collation_name } | { SQL_collation_name }
Arguments
collation_name
Is the name of the collation to be applied to the expression, column 
definition, or database definition. collation_name can be only a specified 
Windows_collation_name or 
a SQL_collation_name. 
Windows_collation_name 
Is the collation name for Windows collation. See Windows Collation Names.
SQL_collation_name 
Is the collation name for a SQL collation. See SQL Collation Names. 
Remarks
The COLLATE clause can be specified at several levels, including the following: 
Creating or altering a database. 
You can use the COLLATE clause of the CREATE DATABASE or ALTER DATABASE statement 
to specify the default collation of the database. You can also specify a collation
when you create a database using SQL Server Enterprise Manager. If you do not 
specify a collation,
 the database is assigned the default collation of the SQL Server instance.
Creating or altering a table column. 
You can specify collations for each character string column using the COLLATE clause
of the CREATE TABLE or ALTER TABLE statement. You can also specify a collation when 
you create a table using SQL Server Enterprise Manager. If you do not specify a 
collation, the column is assigned the default collation of the database.
You can also use the database_default option in the COLLATE clause to specify that a
 column in a temporary table use the collation default of the current user database 
for the connection instead of tempdb.
Casting the collation of an expression. 
You can use the COLLATE clause to cast a character expression to a certain collation.
Character literals and variables are assigned the default collation of the current
database. Column references are assigned the definition collation of the column.  
For the collation of an expression, see Collation Precedence.
The collation of an identifier depends on the level at which it is defined. 
Identifiers of instance-level objects, such as logins and database names, are assigned
 the default collation of the instance. Identifiers of objects within a database, 
such as tables, views, and column names, are assigned the default collation of the 
database. For example,
 two tables with names differing only in case may be created in a database with 
case-sensitive collation, but may not be created in a database with case-insensitive collation.
Variables, GOTO labels, temporary stored procedures, and temporary tables can be 
created when the connection context is associated with one database, and then 
referenced when the context has been switched to another database. The identifiers
 for variables, GOTO labels, temporary stored procedures, and temporary tables are 
in the default collation of the instance.
The COLLATE clause can be applied only for the char, varchar, text, nchar, nvarchar, 
and ntext data types.
Collations are generally identified by a collation name. The exception is in Setup 
where you do not specify a collation name for Windows collations, but instead specify
the collation designator, and then select check boxes to specify binary sorting or 
dictionary sorting that is either sensitive or insensitive to either case or accents.
You can execute the system function fn_helpcollations to retrieve a list of all the 
valid collation names for Windows collations and SQL collations:
SELECT *FROM ::fn_helpcollations()
SQL Server can support only code pages that are supported by the underlying operating
 system. When you perform an action that depends on collations, the SQL Server 
collation used by the referenced object must use a code page supported by the 
operating system running on the computer. These actions can include: 
Specifying a default collation for a database when you create or alter the database.
Specifying a collation for a column when creating or altering a table.
When restoring or attaching a database, the default collation of the database and the
 collation of any char, varchar, and text columns or parameters in the database must
be supported by the operating system. 
Code page translations are supported for char and varchar data types, but not for text
 data type. Data loss during code page translations is not reported.
If the collation specified or the collation used by the referenced object, uses a code
 page not supported by Windows&reg;, SQL Server issues error. For more information, see
 the Collations section in the SQL Server Architecture chapter of the SQL Server Books 
Online.

You can also use the database_default option in the COLLATE clause 
to specify that a column in a temporary table use the collation default of the current
 user database for the connection instead of tempdb.