Manolis Christodoulou wrote:
I would use a char(4) field (fixed length) as a primary key. It would
serve both as an ID and at the same time would have been
informational, and I think fix length strings are faster than varchars.
Just wondering on this - CHAR(4) vs VARCHAR(4) is one *faster* then the
other. Conventional thinking says yes, for in RDBMS systems such as
Oracle, Sybase, MS SQL that was indeed the case - but does that hold
true for HSQLdb? I don't know that answer to that although my
inclination is that it is not the case, in fact it may be just the
opposite even.
Here is a quote from the HSQLdb documentation:
Prior to 1.7.2, all table column type definitions with a column size,
precision or scale qualifier were accepted and ignored.
In 1.8.0, such qualifiers must conform to the SQL standards. For
example INTEGER(8) is no longer acceptable. The qualifiers are still
ignored unless you set a database property. SET PROPERTY
"sql.enforce_strict_size" TRUE will enforce sizes for CHARACTER or
VARCHAR columns and pad any strings when inserting or updating a
CHARACTER column. The precision and scale qualifiers are also enforced
for DECIMAL and NUMERIC types. TIMESTAMP can be used with a precision
of 0 or 6 only.
So I wonder is there any difference is storage mechanism for a CHAR vs
VARCHAR as there is in some other DBMSs?
Anyway - one of those things worth investigating when time permits I
suppose.
Drew
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