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cs.select(x;f)

Read（768） Label: cursor, push,

Description:

Attach the record filtering action to a cursor and return the original cursor while writing records that not satisfy the specified expression to a bin file.

Syntax:

cs.select(x;f)

Note:

The function attaches a record filtering action to cursor cs, which will compute expression x over each record of cursor cs, get records that make value of x true, return the original cursor cs and write the records that do not satisfy expression x into bin file f.

 

This is a delayed function.

Parameter:

cs

A cursor

x

A Boolean expression

f

A bin file

Return value:

Cursor

Example:

 

A

 

1

=demo.cursor("select * from dept")

Return a cursor:

2

=file("dept.btx")

Generate a bin file object.

3

=A1.select(DEPTID<5;A2)

Attach a computation to cursor A1, which will get records that meet DEPTID <5, return cursor A1 and write records that cannot meet the condition to bin file dept.btx:

4

=A1.fetch()

dept.btx will be really generated after data is really fetched out from cursor A1; below is data in cursor A1 where the computation is executed (it would be better that data is fetched in batches when data amount is large):