将 3 列长表转换为具有可变列数的紧凑“2D”表的操作的正确名称是什么？

Question

For example, from this table

row	col	val
0	A	32
0	B	31
0	C	35
1	A	30
1	B	29
1	C	29
2	A	15
2	B	14
2	D	18
3	A	34
3	B	39
3	C	34
3	D	35

it should produce this table:

	A	B	C	D
0	32	31	35
1	30	29	29
2	15	14		18
3	34	39	34	35

Is there some official, canonical (or at least popular specific unambiguous) term for such operation (or its reverse)?

I am trying to find (or implement & publish) a tool that transforms CSV this way, but am unsure what to search for (or how to name it).

Answer 1

The term is pivot .

Some databases have native support for pivot, eg SQL Server's PIVOT (and even UNPIVOT ) keywords.

For most databases you must craft a query that does the job.