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When to use CHAR and VARCHAR
Abstract: When to use CHAR and VARCHAR
Problem:
When to use CHAR and VARCHAR
Solution:
As a guideline:
The rule for CHAR and VARCHAR is to use CHAR only for strings
whose length you know to be fixed. For example, if you define a domain
whose values are restricted to 'T' and 'F', you should probably make
that CHAR[1]. If you're storing US social security numbers, make the
domain CHAR[9] (or CHAR[11] if you want punctuation).
Use VARCHAR for strings that can vary in length, like names, short
descriptions, etc. Use VARCHAR when you don't want to worry about
stripping trailing blanks. Use VARCHAR unless there's a good reason
not to.
Use CHAR when you're defining external tables. VARCHAR includes a
two-byte binary prefix that contains the effective length of the string.
That's a nuisance in an external file - your text editor won't like it
at all.
Source: Ann Harrison Mers listserve
