id()
Here’s how to use id() function.
A .id()
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:
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xi |
An expression; use ~ to represent x if the latter is omitted |
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n |
The number of to-be-retrieved distinct values counting from the beginning; return all values if it is absent |
Option:
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@o |
Without sorting, remove the neighboring duplicate members only |
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@u |
Do not sort the result set by x; it doesn’t work with @o |
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@h |
Used over a grouped table with each group ordered to speed up grouping |
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@0 |
Discard members on which expression x is computed and gets empty result |
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@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 |
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@n |
Judge whether a member is distinct or not according to position when there is only one xi and xi is a natural number |
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@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:
The new sequence composed of the distinct values of x
Example:
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A |
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1 |
=demo.query("select * from EMPLOYEE") |
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2 |
=A1.id(DEPT) |
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3 |
=A1.id@o(DEPT) |
No sorting |
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4 |
=A1.id([DEPT,GENDER]) |
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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 |
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6 |
=A1.id@u([DEPT,GENDER]) |
Do not sort the result set by x |
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7 |
=A1.id(DEPT,GENDER) |
Return all distinct values as parameter n is absent
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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
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9 |
=file("D:/emp10.txt").import@t() |
For data file emp10.txt, every 10 records are ordered by DEPT |
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10 |
=A9.id@h(DEPT) |
As A19 is grouped and ordered by DEPT, @h option is used to speed up grouping
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A |
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1 |
=demo.query("select * from DEPT") |
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2 |
=A1.id(FATHER) |
Return value: [null,1,2,11,12] |
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3 |
=A1.id@0(FATHER) |
Return value: [1,2,11,12] |
Related function:
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 |
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xi |
Expression; use comma to separate multiple expressions |
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n |
Integer; can’t be omitted |
Return value:
Channel
Example:
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A |
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1 |
=demo.cursor("select EID,NAME,DEPT,SALARY from EMPLOYEE") |
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2 |
=channel() |
Create a channel |
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3 |
=channel() |
Create a channel |
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4 |
=A2.id(#1,DEPT;10) |
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5 |
=A3.id(DEPT;5) |
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6 |
=A1.push(A2,A3) |
Push data in A1’s cursor into A2’s channel and A3’s channel |
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7 |
=A1.fetch() |
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8 |
=A2.result() |
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9 |
=A3.result() |
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cs .id()
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 |
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xi |
An expression; use comma to separate multiple expressions |
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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 |
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@u |
Do not sort result set by expression x; the option and @o are mutually exclusive |
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@h |
Used to segment ordered data, which increases efficiency |
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@0 |
Discard members on which expression x is computed and gets empty result |
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@n |
Judge whether a member is distinct or not according to position when there is only one xi and xi is a natural number |
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@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:
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A |
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1 |
=demo.cursor("select * from EMPLOYEE" ) |
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2 |
=A1.id(#1,DEPT;5) |
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3 |
=demo.cursor("select * from EMPLOYEE" ) |
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4 |
=A3.id(DEPT;5) |
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5 |
=demo.cursor("select * from EMPLOYEE" ).sortx(DEPT).id@o(DEPT) |
Do not sort records, but remove the neighboring duplicate records only
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6 |
=demo.cursor("select * from EMPLOYEE" ).id@u(DEPT) |
Do not sort result set by DEPT
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A |
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1 |
=demo.cursor("select * from DEPT") |
Below is content of DEPT table:
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2 |
=A1.id(FATHER) |
Return value: [null,1,2,11,12] |
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3 |
=A1.reset() |
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4 |
=A1.id@0(FATHER) |
Return value: [1,2,11,12] |
