T.cursor(x:C,…;wi…;k:n)

@m

The T.cursor@m(x:C…;wi,...;n) function with this option generates a multicursor segmented into n parts. n is an integer; the function returns an ordinary cursor if n<2; use the value of【Default number of subcursors in a multicursor】 set in【Tool】-【Options】if n is absent.

@v

Generate a pure table sequence-based columnwise cursor, which has higher performance than regular cursors.

@x

Automatically close the entity table/in-memory table after data in the cursor is fetched.

@g

When T is a multizone composite table and if group() operation will be executed on the result cursor, use this option to speed up the computation.

@w

Used on a multizone composite table with update mark;

Perform update merge; when zone tables share a same key value, ignore the record contained in the zone table with a smaller number; segmentation is performed according to the way zone table 1 is split;

Handle the update mark and do not return records with a deletion mark to the cursor; but if the key value of a record with the deletion mark is unique in the multizone composite table, just retain it;

This option enables retrieving key field(s) as well as the deletion mark field, if there is one, forcefully.

@z

Get data in the inverse order; do not support segmentation in this case.

T

An entity table or an in-memory table or a multizone composite table

x

Expression; by default, all fields of T will be returned to the cursor

C

Column alias; can be omitted

wi

Filtering condition; separate multiple conditions by comma(s) and their relationships are AND; besides regular filtering expressions, you can also use the following five types of syntax in a filtering condition, where K is a field in the entity table:

1．K=w

w usually uses expression T_i.find(K) or T_i.pfind(K), where T_i is a table sequence. When value of w is null or false, the corresponding record in the entity table will be filtered away; when w is expression T_i.find(K) and the to-be-selected fields C,... contain K, T_i’s referencing field will be assigned to K; when w is expression T_i.pfind(K) and the to-be-selected fields C,... contain K, sequence numbers of K values in T_i will be assigned to K.

2．(K₁=w₁,…K_i=w_i,w)

K_i=w_i is an assignment expression. Generally, parameter w_i can use expression T_i.find(K_i) or T_i.pfind(K), where T_i is a table sequence; when w_i is expression T_i.find(K) and the to-be-selected fields C,... contain K_i, T_i’s referencing field will be assigned to K_i correspondingly; when w_i is expression T_i.pfind(K_i) and the to-be-selected fields C,... contain K_i, sequence numbers of K_i values in T_i will be assigned to K_i.

w is a filter expression; you can reference K_i in w.

3．K:T_i

T_i is a table sequence. Compare K_i value in the entity table with key values of T_i and discard records whose K_i value does not match; when the to-be-selected fields C,... contain K, T_i’s referencing field will be assigned to K.

4．K:T_i:null

Filter away all records that satisfy K:T_i.

5．K:T_i:#

Locate records according to sequence numbers, compare sequence numbers of records in table sequence T_i according to the entity table’s K values, and discard non-matching records; when the to-be-selected fields C,... contain K, T_i’s referencing field will be assigned to K

k

A positive integer (k≤n) representing the k^th segment

n

A positive integer representing the number of segments; return all records when parameters k:n are absent

A

1

for 100

2

=to(10000).new(#:k1,rand():c1).sort@o(k1)

Return a table sequence:

3

=to(10000).new(#:k1,rand(10000):c2,rand()*1000:c3).sort@o(k1)

Return a table sequence:

4

=A2.cursor()

Return a cursor.

5

=A3.cursor()

Return a cursor.

6

=file("D:\\tb4.ctx")

Generate a composite table file.

7

=A6.create(#k1,c1)

Create A6’s base table whose key is k1.

8

=A7.append(A4)

Append data of A4’s cursor to A7’s base table.

9

=A7.attach(table4,c2,c3)

Create an attached table table4 for the base table.

10

=A9.append(A5)

Append data of A5’s cursor to attached table table4.

11

=A9.cursor(;c2<1000;2:3)

Divide records meeting c2<1000 in the attached table into 3 segments and return a cursor of all columns of the second segment.

12

=A11.fetch()

Fetch data from A11’s cursor.

13

=A7.cursor(;c1>0.99)

Get records meeting c1>0.99 from A7’s base table

14

=A13.fetch()

Fetch data from A13’s cursor.

b

15

=A9.cursor(k1,c1:b,c3;c3>999)

Get the base table’s k1 field and c1 field from attached table table4, as well as c3 field of the attached table, according to condition c3>999, and rename c1 b.

16

=A15.fetch()

Fetch data from A15’s cursor.

17

=A9.cursor@m(;;3)

Use @m option to generate a multicursor from attached table table4.

A

1

=file("employee1.ctx")

Generate composite table file employee1.ctx.

2

=A1.create@y(#EID,NAME,GENDER,SALARY)

Create the base table of composite table employee1.ctx, which contains columns EID, NAME, GENDER and SALARY and where EID is the dimension.

3

=connect("demo").cursor("select  EID,NAME,GENDER,SALARY  from  employee")

Return a cursor.

4

=A2.append@i(A3)

Append records of A3’s cursor to A2’s base table.

5

=A2.cursor@v(;SALARY>1000;)

Return a column-wise cursor, and automatically close A2’s composite table after data is fetched from it.

6

=A5.groups(GENDER;avg(SALARY):SALARY_AVG)

Perform grouping & aggregation operation on A5’s cursor.

7

=A2.cursor(;SALARY>2000)

Error is reported, prompting“Stream Closed” .

A

1

=100000.new(~:ID,rand(2):FM).cursor()

2

=file("nc.ctx":[1,2])

Generate a homo-names files group.

3

=A2.create@y(#ID,FM;if(FM==1,1,2))

Return a multizone composite table.

4

=A3.append@x(A1)

Append cursor A1’s data to the multizone composite table; below is content of the multizone composite table:

1.nc.ctx  2.nc.ctx

5

=A3.cursor(;;1:3)

Split the multizone composite table into three segments, return the first segment of each zone table, merge them and return result as a cursor:

Data in zone table 1 and that in zone table 2 has been merged by their dimensions.

A

1

=file("emp.ctx")

2

=A1.open()

Open the composite table file.

3

=A2.import()

As no parameters are present, return all data in the entity table.

4

=5.new(~:ID,~*~:Num).keys(ID)

Generate a table sequence using ID as the key.

5

=A2.cursor(EID,NAME;EID=A4.find(EID))

Use K=w filtering mode; in this case w is T_i.find(K) and entity table records making EID=A4.find(EID) get null or false are discarded; EID is the selected field, to which table sequence A4’s referencing field are assigned.

6

=A2.cursor(EID,NAME;EID=A4.pfind(EID))

Use K=w filtering mode; in this case w is T_i.pfind(K) and entity table records making EID=A4.pfind(EID) get null or false are discarded; EID is the selected field, to which its sequence numbers in table sequence A4 is assigned.

7

=A2.cursor(EID,NAME;EID:A4)

Use K:T_i filtering mode; compare the entity table’s EID values with the table sequence’s key values and discard entity table records that cannot match.

8

=A2.cursor(NAME,SALARY;EID:A4)

This is a case where K isn’t selected; EID isn’t the selected field, so only filtering is performed.

9

=A2.cursor(EID,NAME;EID:A4:null)

Use K:T_i:null filtering mode; compare the entity table’s EID values with the table sequence’s key values and discard entity table records that can match.

10

=A2.cursor(EID,NAME;EID:A4:#)

Use K:T_i:# filtering mode; compare with sequence numbers of table sequence’s records according to the entity table’s EID values, and discard records that cannot match.

11

=connect("demo").query("select top 2  NAME,GENDER  from employee").keys(NAME)

Return a table sequence using NAME as the key.

12

=A2.cursor(EID,NAME;(EID=A4.find(EID),NAME=A11.find(NAME),EID!=null&&NAME!=null))

Use (K₁=w₁,…K_i=w_i,w) filtring mode; return records that meet all conditions

A

1

=100000.new(~:ID,rand(2):FM)

2

=file("curz.ctx")

3

=A2.create@y(#ID,FM)

Create a composite table.

4

=A3.append@i(A1)

5

=A4.cursor().fetch()

Return the composite table as a cursor and fetch data from the cursor:

6

=A4.cursor@z().fetch()

Use @z option to get data in the inverse order and fetch data from the cursor as follows:

A

1

=connect("demo").cursor("select  EID,NAME,GENDER  from employee") 

2

=A1.derive(:Defiled)

3

=A2.new(EID,Defiled,NAME,GENDER)

Return a cursor whose content is as follows:

4

=file("ecd.ctx":[1,2])

Define a homo-name files group: 1.ecd.ctx and 2.ecd.ctx.

5

=A4.create@yd(#EID,Defiled,NAME,GENDER;if(GENDER=="F",1,2))

Create a multizone composite table, set EID as the key, use @d option to make Defiled field the update mark and put records where GENDER is F to 1.ed.ctx and the other records to 2.ed.ctx.

6

=A5.append@ix(A3)

Append cursor A3’s data to the multizone composite table.

7

=create(EID,Defiled,NAME,GENDER).record([0,true,,,1,true,,,

2,false,"BBB","F"])

Return a table sequence whose content is as follows:

8

=file("ecd.ctx":[3])

9

=A8.create@yd(#EID,Defiled,NAME,GENDER;3)

Add zone table 3.ecd.ctx and make Defiled the update mark field.

10

=A9.append@i(A7)

Append table sequence A7’s records to zone table 3.ecd.ctx.

11

=file("ecd.ctx":[1,2,3]).open()

Open composite table file ecd.ctx.

12

=A11.cursor().fetch()

Return all data in the multizone composite table ecd.ctx to the cursor; below is the returned content:

13

=A11.cursor@w().fetch()

With @w option, return data in multizone composite table ecd.ctx as a cursor and recognize the update mark:

Do not return the record whose EID value is 2 and where the update mark value is true (meaning to-be-deleted) to the cursor;

Update the record where EID value is 2 and marked by false (meaning to-be-modified);

Retain the record where EID value is 0, marked by true (meaning to-be-deleted), and whose key value is unique, and return it to the cursor; Below is content of the returned cursor: