How does SQL server compress NULL bit datatypes?

Question

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Can Microsoft store three-valued fields in a single bit?

According to the documentation for bit, the bit datatype can have three values, 0, 1 and NULL and if there are 8 or less bit columns in a table, those columns will be compressed into one byte.

These two behaviors seem contradictory. If so, which part is correct, the ability of a bit to be NULL or the compression of 8 bits to a byte?

I would hazard a guess that this only applies to non-nullable BIT columns. — Lasse V. Karlsen, Feb 23 '11 at 15:42

score 2 · Answer 1 · answered Feb 23 '11 at 15:44

2

NULL values are handled by a separate bit for each column (for example look here for details).

answered Feb 23 '11 at 15:44

TToni

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How does SQL server compress NULL bit datatypes?

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