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T.select()

Read（313） Label: pseudo table, filter condition, index,

Description:

Define a record filtering operation on a pseudo table and return a new pseudo table.

Syntax:

T.select(x)

Note:

The function defines a computation on pseudo table T, which will calculate expression x on each of its records and get records that make x true, and return a new pseudo table.

 

It returns a pseudo table retaining all records when parameter x is absent.

Parameter:

T

A pseudo table

x

A Boolean expression that is a filter condition, which can be null

Return value:

Pseudo table object

Example:

 

A

 

1

=create(file).record(["D:/file/pseudo/app.ctx"])

Below is data in composite table app.ctx:

2

=pseudo(A1)

 

Generate a pseudo table object.

3

=A2.select(eid>7)

Define a computation on A2’s pseudo table, which will get records that satisfy eid>7, and return a new pseudo table.

4

=A3.import()

Import data from A3’s pseudo table while executing the computation defined in A3 on A2’s pseudo table, and return the following table:

5

=A2.select()

Define a computation on A2’s pseudo table, which will get all records, and return a new pseudo table.

6

=A5.import()

Import data from A5’s pseudo table while executing the computation defined in A5 on A2’s pseudo table, and return the following table: