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Questionchar(255) vs varchar(255) vs varchar(MAX) Pin
devvvy1-Feb-13 18:22
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GeneralRe: char(255) vs varchar(255) vs varchar(MAX) Pin
devvvy2-Feb-13 15:39
memberdevvvy2-Feb-13 15:39 
I did but not sure if I interpreted MSDN correctly.
<br />
<br />
char [ ( n ) ]<br />
<br />
    Fixed-length, non-Unicode string data. n defines the string length and must be a value from 1 through 8,000. The storage size is n bytes. The ISO synonym for char is character.<br />
varchar [ ( n | max ) ]<br />
<br />
    Variable-length, non-Unicode string data. n defines the string length and can be a value from 1 through 8,000. max indicates that the maximum storage size is 2^31-1 bytes (2 GB). The storage size is the actual length of the data entered + 2 bytes. The ISO synonyms for varchar are char varying or character varying.


varchar(255) --- this means SQL server will always allocate 255bytes? Or depending on actual values being inserted for a particular row?

If say row 1, "Name" = 25 bytes and row 2, "Name" = 225 bytes (say no other row longer than 225), then...
POSSIBILITY 1: SQL server always allocate 225 bytes (actual length of data, taken from row 2)
POSSIBILITY 2: SQL server always allocate 255 bytes for all rows as defined in column definition varchar(255)
POSSIBILITY 3: SQL Server allocate 25 bytes for row 1, and 225 bytes for row 2 (actual length of data vary from one row to the next)

My guess is - POSSIBILITY 3 is how SQL server actually behalves. This said, then why we bother specify varchar(n)? We should always specify varchar(MAX). Two reasons I can think of after a bit of digging...[^]

a. You cannot index anything varchar longer than 900 bytes
b. by MAX, you remove column max length validation provided for you at database level.

Am I missing something?
dev


modified 2-Feb-13 21:55pm.

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QuestionEncrypt a field in the database. Pin
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Questioncheck before insert Pin
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