id()

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Here’s how to use id() function.

A.i d()

Description:

Get distinct values from a sequence.

Syntax:

A.id(xi,…;n)

Note:

The function gets top n distinct values of the expressions xi,…. If the number of distinct values in an expression x is less than n, return all distinct values as a sequence; the result set consists of one ordinary sequence when there is only one expression x.

Parameter:

xi

An expression; use ~ to represent x if the latter is omitted

n

The number of to-be-retrieved distinct values counting from the beginning; return all values if it is absent

Option:

@o

Without sorting, remove the neighboring duplicate members only

@u

Do not sort the result set by x; it doesn’t work with @o

@h

Used over a grouped table with each group ordered to speed up grouping

@0

Discard members on which expression x is computed and gets empty result

@m

Enable parallel processing to increase performance of complex computations on a large volume of data, with indefinite computing order; the parameter and @o option are mutually-exclusive

@n

Judge whether a member is distinct or not according to position when there is only one xi and xi is a natural number

@b

Judge whether a member is distinct or not according to the bit length in a byte in order to reduce storage usage when there is only one xi and xi is a natural number

Return value:

Sequence

Example:

 

A

 

1

=demo.query("select * from EMPLOYEE")

 

2

=A1.id(DEPT)

Sort members in ascending order.

3

=A1.id@o(DEPT)

No sorting.

4

=A1.id([DEPT,GENDER])

 

Get the distinct values after sorting by DEPT & GENDER.

5

=["a","b","c","a"].id()

Omitting x indicates it is the sequence members themselves that will be computed to get the distinct values. Return ["a","b","c"] as with this case.

6

=A1.id@u([DEPT,GENDER])

Do not sort the result set by x.

7

=A1.id(DEPT,GENDER)

Return all distinct values as parameter n is absent.

 

8

=A1.id(DEPT,GENDER;4)

Return the first 4 distinct values; return all GENDER values as the field has less than 4 distinct values.

9

=file("D:/emp10.txt").import@t()

For data file emp10.txt, every 10 records are ordered by DEPT.

10

=A9.id@h(DEPT)

As A19 is grouped and ordered by DEPT, @h option is used to speed up grouping.

 

 

A

 

1

=demo.query("select * from DEPT")

2

=A1.id(FATHER)

Return value: [null,1,2,11,12].

3

=A1.id@0(FATHER)

Return value: [1,2,11,12] .

Related function:

A.group(xi,)

ch.id ()

Description:

Generate a channel consisting of values of one or more fields.

Syntax:

ch.id(xi,…;n)

Note:

The function generates a channel containing a sequence of sequences, each of which is made up of values of xi field in channel ch. Get at most n values for each xi field; return a channel containing one sequence when there is only one xi field. It is for getting the result set from the channel.

Parameter:

ch

Channel

xi

Expression; use comma to separate multiple expressions

n

Integer; can’t be omitted

Return value:

Channel

Example:

 

A

 

1

=demo.cursor("select EID,NAME,DEPT,SALARY from EMPLOYEE")

 

2

=channel()

Create a channel.

3

=channel()

Create a channel.

4

=A2.id(#1,DEPT;10)

 

5

=A3.id(DEPT;5)

 

6

=A1.push(A2,A3)

Push data in A1’s cursor into A2’s channel and A3’s channel.

7

=A1.fetch()

 

8

=A2.result()

9

=A3.result()

cs.i d()

Description:

Generate a sequence consisting of values of fields in a given cursor.

Syntax:

cs.id(xi,…;n)

Note:

The function generates a sequence of sequences, each of which is made up of values of xi field in cursor cs. Get at most n values for each xi field; return a sequence when there is only one xi field.

Parameter:

cs

A cursor

xi

An expression; use comma to separate multiple expressions

n

An integer; return all values when omitted

Option:

@o

Do not sort data while removing neighboring duplicate members; require that data is ordered by expression x

@u

Do not sort result set by expression x; the option and @o are mutually exclusive

@h

Used to segment ordered data, which increases efficiency

@0

Discard members on which expression x is computed and gets empty result

@n

Judge whether a member is distinct or not according to position when there is only one xi and xi is a natural number

@b

Judge whether a member is distinct or not according to the bit length in a byte in order to reduce storage usage when there is only one xi and xi is a natural number

Return value:

Sequence

Example:

 

A

 

1

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

 

2

=A1.id(#1,DEPT;5)

3

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

 

4

=A3.id(DEPT;5)

5

=demo.cursor("select * from EMPLOYEE" ).sortx(DEPT).id@o(DEPT)

Do not sort records, but remove the neighboring duplicate records only.

6

=demo.cursor("select * from EMPLOYEE" ).id@u(DEPT)

Do not sort result set by DEPT.

 

 

A

 

1

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

Below is content of DEPT table:

2

=A1.id(FATHER)

Return value: [null,1,2,11,12] .

3

=A1.reset()

 

4

=A1.id@0(FATHER)

Return value: [1,2,11,12] .