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gus bjorklund
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> On Nov 13, 2019, at 6:53 AM, mboubidi wrote: > > Sequence Name: Are these represent tables or Columns of table? > > quick overview of sequences: sequences are integer /number generators/. they are independent entities not associated with any table but the sequence values can be used to form keys in tables and for other purposes. when you request the /next value/ from a sequence, you get back an integer that is higher than the current value by whatever the increment is set at. or lower if the increment value is negative. the value given to you is guaranteed to be yours and will not be given to anyone else (exception: if the generator is (optionally) allowed to recycle and start over when it reaches the end of its range). the next request for the next value will produce the next higher (or lower) value. these number generators are meant to be efficient and durable and can be safely used in transactions. there is one drawback: the sequence may have a gap if a crash occurs. this is because crash recovery cannot undo sequence operations. that is a deliberate design decision, not a bug.
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