char与nchar区别..(国外英文资料).docVIP

char与nchar区别..(国外英文资料) 1, char and nchar similar to the char data type to store fixed length character, the longest can accommodate 8000 characters definition is: char[(n)], which n said, all the characters occupy storage space, in bytes. N must be a value between 1-8000. If not specified, the system defaults to 1. By using char, if the set length is less than the actual length, more than the characters will be truncated; otherwise, if the set length is greater than the actual length, then the extra bytes will be filled with spaces. For nchar to define fixed length Unicode data, the maximum length is 4000 characters. The definition is similar to char. The difference is that because of the nchar type, the Unicode standard data type takes up more than twice the storage space. The advantage of using the Unicode standard is that the capacity of one storage unit is greatly increased because of the two bytes it uses as storage units. 2, varchar is similar to nvarchar, and their differences are similar to those of char and nchar. The difference is in the storage space. The former is set, the characters are large, and the storage space is large Varchar (n) Variable length and non Unicode character data of N bytes in length. N must be a value between 1 and 8000. The actual length of the byte in which the storage size is the input data, not the n byte. Nvarchar (n) Variable length Unicode character data containing n characters. The value of N must be between 1 and 4000. The storage size of bytes is two times the number of characters entered. The two fields have field values respectively: I and coffee Then, the varchar field occupies 2 * 2+6=10 bytes of storage space, while the nvarchar field occupies 8 * 2=16 bytes of storage space. If the field value is only English, you can choose varchar, and the field value exists more double bytes (Chinese, Korean, etc.) characters, using nvarchar The above is a summary of the introduction, through the above introduction, you can know.