T.icursor()

Read(317) Label: index, entity table,

Description:

Use index to filter an entity table or a multi-zone composite table according to the filtering condition.

Syntax:

T.icursor(C,…;w,I)

Note:

The function filters entity table or multi-zone composite table T according to filtering condition w using index I and automatically gets the index if parameter I is absent.

Perform the filtering on each zone table using the corresponding index separately when parameter T is a multi-zone composite table. It is not required that each zone table have the index; perform traversal if one does not have an index.

Parameters:

T

An entity table or a multi-zone table

C

To-be-retrieved columns in the entity table; get all columns when the parameter is absent

w

Filtering condition, in which the filtering field for T must be the same as the indexing fiel; support >, >=, <, <=, == and contain in its syntax

I

Index name; can be omitted

Options:

@s

Make sure the result set is ordered by the index and large result sets are supported

@u

Handle multiple conditions joined up with && from left to right while the default is handling them in an optimal order

Return value:

A single-thread cursor

Example:

 

A

 

1

=file("D:\\emp1.ctx")

 

2

=A1.create(#EID,NAME,DEPT,GENDER)

Create the composite table’s base table

3

=demo.cursor("select EID,NAME,DEPT,GENDER from employee where EID<100")

 

4

=A2.append(A3)

 

5

=A4.index(test_index,GENDER=="F";DEPT;EID)

Create an index named test_index

6

=A4.icursor(;DEPT=="HR",test_index)

Use index test_index to get all columns where DEPT is HR and return the result as a cursor

7

=A5.fetch()

Fetch data from the cursor

 

8

=A4.icursor@u(;like(DEPT,"*ale*")&&EID>=50,test_index).fetch()

Handle the multiple conditions connected by && from left to right; use index test_index to find records where DEPT values containing “ale” and EID is greater and equal to 50

9

=file("emp.ctx":[2,3])

Return a homo-name files group

10

=A9.open()

Open A9’s multi-zone composite table

11

=A10.index(index_cp,SALARY>10000;GENDER;)

Create index index_cp for A10’s multi-zone composite table

12

=A10.icursor(;GENDER=="F",index_cp).fetch()

Use the index to get records where GENDER is F