NULL Values

• NULL means "a missing unknown value".
  • It is treated somewhat differently from other values.
    • Arithmetic comparison operators such as =, <, <>, cannot be used.
    • Use the IS NULL and IS NOT NULL operators instead.
    • Use column_name IS NOT NULL instead of column_name <> NULL.
    • NULL values are presented first if ORDER BY ... ASC and last if ORDER BY ... DESC.

How does MySQL handle pattern matching?

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© 2007 John Michael Pierobon

Notes