Pour SQL Server, ils sont conformes à SQL 92, ainsi que nchar et nvarchar (caractères unicodes)
char and varchar
Fixed-length (char) or variable-length (varchar) character data types.
char[(n)]
Fixed-length non-Unicode character data with length of n bytes. n must be a value from 1 through 8,000. Storage size is n bytes. The SQL-92 synonym for char is character.
varchar[(n)]
Variable-length non-Unicode character data with length of n bytes. n must be a value from 1 through 8,000. Storage size is the actual length in bytes of the data entered, not n bytes. The data entered can be 0 characters in length. The SQL-92 synonyms for varchar are char varying or character varying.
Remarks
When n is not specified in a data definition or variable declaration statement, the default length is 1. When n is not specified with the CAST function, the default length is 30.
Objects using char or varchar are assigned the default collation of the database, unless a specific collation is assigned using the COLLATE clause. The collation controls the code page used to store the character data.
Sites supporting multiple languages should consider using the Unicode nchar or nvarchar data types to minimize character conversion issues. If you use char or varchar: Use char when the data values in a column are expected to be consistently close to the same size.
Use varchar when the data values in a column are expected to vary considerably in size. If SET ANSI_PADDING is OFF when CREATE TABLE or ALTER TABLE is executed, a char column defined as NULL is handled as varchar. When the collation code page uses double-byte characters, the storage size is still n bytes. Depending on the character string, the storage size of n bytes may be less than n characters.
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On note d'ailleurs que SQL Server est pas beaucoup mieu que MySQL pour le coup du changement de type sans rien dire
M'enfin bon, ça n'arrive que dans un cas très précis, et c'est documenté (et faut être un gros boulet pour pas le trouver dans la doc)
Par contre, c'est dans l'autre sens
Bon, après, ça dépends de la façon dont le système gère les deux types...
Message édité par MagicBuzz le 19-08-2003 à 21:58:49