create()

Read(4636) Label: create,

Here’s how to use create() functions.

create ()

Description:

Create an empty table sequence.

Syntax:

create(Fi,…)

Note:

The function creates an empty table sequence taking Fi,… as its fields.

Parameter:

Fi

Field name

Return value:

An empty table sequence

Example:

 

A

 

1

=create(id,name,gender)

create(#Fi,…)

Description:

Create an empty table sequence with one or more keys set.

Syntax:

create(#Fi,…) 

Note:

The function creates an empty table sequence consisting of fields Fi,…. A field name headed by a hash (#) is a key. For the time being, the function cannot generate a time key directly.

Parameter:

Fi

Field name

Return value:

Empty table sequence

Example:

 

A

 

1

=create(#id,#name,gender)

id field and name field are keys.

f.create(C,…; x;b)

Description:

Create a composite table based on a file.

Syntax:

f.create(C,…;x;b)

Note:

The function creates a composite table using composite table file f and generates a multizone composite table if f is a homo-name files group. Parameter C is a column, which is a dimension if it is preceded by #, of the would-be composite table, and parameter x is a zone table expression. The dimension and all fields before it must be ordered.

Parameter:

f

A composite table file object or a homo-name files group object

C

A column of the would-be composite table

x

A zone table expression, whose result is the integer representing the corresponding zone table

b

Block size, whose unit is byte. Default value is the “Composite table block size” configured in the configuration options; when esProc is integrated into a third-party application, the parameter’s default value is value of blockSize configured in raqsoftConfig.xml file

Option:

@u

Do not compress the file; default is to compress it

@r

Generate a row-wise file while default is columnar storage, which does not support the multicursor

@y

Force to re-create the file even if the target file already exists; defalut is to terminate computation

@p

Use the first field as the grouping key

@v

When columnar storage is used to generate the composite table, check whether each of its columns is pure during data maintenance and save the data type

@t

Create key for the composite table (including multizone composite table) using dimensions and the last key field is the time key; in this case no attached table is allowed

@d

Used on a multizone composite table; the first field after key fields is regarded as the deletion mark field, whose values are Boolean type; a deletion mark value that is true means the record is deleted and is used for judging whether the current record is deleted or not when data is retrieved from a multizone composite table

Return value:

A composite table or a homo-name files group

Example:

 

A

 

1

=file("employee1.ctx")

Generate composite table file employee1.ctx.

2

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

Create A1’s base table whose columns are EID, NAME and GENDER; EID is the dimension.  

3

=connect("demo").cursor("select EID,NAME,GENDER,SALARY  from employee where GENDER='M' order by SALARY")

 

4

=connect("demo").cursor("select EID,NAME,GENDER,SALARY  from employee where GENDER='F' order by SALARY")

 

5

=[A3,A4].mcursor()

Return a multicursor.

6

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

Generate a homo-name files group, which contains two files 1.emp.ctx and 2.emp.ctx.

7

=A6.create@y(#EID,NAME,GENDER,SALARY;if(GENDER=="F",1,2))

Create a multizone composite table; if(GENDER=="F",1,2) is zone table expression and @y forces to re-create the target file even if it already exists.

8

=A7.append@i(A5)

Append data in A5’s multicursor to A7’s multizone composite table; each part of the multicursor uniquely corresponds to A7’s one zone table.

9

=file("1.emp.ctx").open().cursor().fetch()

View data in zone table 1.emp.ctx.

10

=file("2.emp.ctx").open().cursor().fetch()

View data in zone table 2.emp.ctx.

Use the first field as the segmentation key:

 

A

 

1

=file("CITIES.ctx")

Generate composite table file CITIES.ctx.

2

=A1.create@p(STATEID,#CID,NAME,POPULATION)

Create the base table of CITIES.ctx and use @p option to make the first field STATEID the grouping key; when the option is absent, use dimension field CID as the default grouping field.

Set the time key:

 

A

 

1

=file("transaction.ctx")

 

2

=A1.create@yt(#UID,#Time,Change,Amount)

Create the composite table’s base table; @t option works to set UID as the basic key and Time as the time key.

3

=file("transaction.txt").cursor@t().sortx(UID,Time)

Return a cursor ordered by UID and Time.

4

=A2.append@i(A3)

Append cursor A3’s data to the base table.

5

=A2.import()

Retrieve data of the base table.

When deletion mark field is present:

 

A

 

1

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

 

2

=A1.derive(false:Defiled)

 

3

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

Return a cursor, whose content is as follows:

4

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

Homo-name files group: 1.ed.ctx and 2.ed.ctx.

5

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

Create a composite table, set EID as the key, use @d option to make Defield field the deletion 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 A1’s data to the multizone composite table.

7

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

Return a cursor, whose content is as follows:

8

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

 

9

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

Add a zone table and delete the record whose primary key is 1.

10

=A9.append@i(A7)

Append cursor A7’s data to zone table 3.ed.ctx.

11

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

 

121

=A11.open()

Open A11’s multizone composite table.

13

=A12.cursor@w()

Return the multizone composite table as a cursor, use @w option to handle the deletion mark, which means records where Defiled field values are true are recognized as the to-be-deleted and won’t be retrieved.

14

=A13.fetch()

Fetch data in cursor A13.

We can see that the record where EID is 1 isn’t retrieved from the multizone composite table.

P.create()

Description:

Generate a new empty table sequence by copying data structure of a specific record sequence.

Syntax:

P.create()

Note:

If parameter P has the key, just copy it.

Parameter:

P

A record sequence

Return value:

Empty table sequence

Example:

Generated from a record sequence:

 

A

 

1

=demo.query("select top 1 * from DEPARTMENT")

2

=A1.to()

Generate a record sequence.

3

=A2.create()

Create an empty table sequence that has same data structure as A2’s.

When there is the key:

 

A

 

1

=demo.query("select top 1 * from DEPARTMENT ")

2

=A1.keys(DEPT)

 

3

=A1.to()

Generate a record sequence CITIES.ctx.

4

=A3.create()

Create an empty table sequence that has same data structure as A3’s while copying the key.

T.create ()

Description:

Create an empty table sequence by duplicating data structure of a specific table sequence.

Syntax:

T.create()

Note:

If table sequence T has a key, then duplicate the key at the same time.

Parameter:

T

A table sequence

Return value:

A new empty table sequence

Example:

Created from a normal table sequence :

 

A

 

1

=demo.query("select top 1 * from DEPARTMENT")

2

=A1.create()

 

Create an empty table of same structure as A1.

Copy the key

 

A

 

1

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

2

=A1.keys(DEPT)

 

3

=A1.create()

Create an empty table sequence that has not only the same data structure, but also the same key, as table sequence A1.

T.create(f:b;x)

Description:

Create a new composite table file using the data structure of an existing composite table.

Syntax:

T.create(f:b;x)

Note:

The function creates a new composite table file f using table structure of composite table T, and generates a multizone composite table file when the target f is a homo-name files group. f will include T’s attached tables.

Parameter:

T

A composite table

f

A composite table file or a homo-name files group

b

Block size, whose unit is byte and whose default value is composite table block sizeconfigured through menu option; when esProc is integrated in the third-party application, use blockSize value configured in raqsoftConfig.xml by default

x

An integer, which is zone table expression

Option:

@u

Do not compress data; use compression by default

@r

Generate a row-oriented file while by default generate a column-oriented one; a row-oriented composite table cannot use multicursor; do not compress a row-oriented file

@y

Forcibly to create the file even if a namesake one already exists; by default terminate the computation

Return value:

Composite table

Example:

 

A

 

1

=create(k1,v1).record([1,10,2,20]).cursor()

Return a cursor that has data as follows:

2

=create(k1,k2,v2).record([1,11,111,2,22,222]).cursor()

Return a cursor that has data as follows:

3

=file("ctb.ctx").open()

Open a composite table file that contains an attached table table2.

4

=A3.create@y(file("ctbCp.ctx"))

Create new composite table file ctbCp.ctx, as well as its attached table, using data structure of composite table ctb.ctx; as @y works, forcibly create the file even if ctbCp.ctx already exists.

5

=A4.append@i(A1)

Append data of A1’s cursor to the base table of composite table ctbCp.ctx.

6

=A4.attach(table2)

Open A4’s attached table table2.

7

=A6.append@i(A2)

Append data of A2’s cursor to ctbCp.ctx’s attached table table2.

Use @u option to not to compress the generated composite table file:

 

A

 

1

=file("em.ctx").open()

Open composite table file em.ctx.

2

=A1.create@yu(file("ctbCp2.ctx"))

Create a non-compressed composite table file ctbCp2.ctx using the existing composite table file em.ctx.

3

=file("ctbCp2.ctx").structure()

View structure of the composite table file ctbCp2.ctx; the false zip value means non-compression:

Use @r option to generate a row-oriented file:

 

A

 

1

=file("em.ctx").open()

Open composite table file em.ctx.

2

=A1.create@yr(file("ctbCp3.ctx"))

Create a row-oriented composite table file ctbCp3.ctx using the existing composite table file em.ctx.

3

=file("ctbCp3.ctx").structure()

View structure of the composite table file ctbCp3.ctx; the true row value represents row-oriented file:

r.create()

Description:

Create a table sequence by copying the data structure of a specified record.

Syntax:

r.create()

Note:

If there’s a key defined in record r, then copy the key at the same time.

Parameter:

r

A record

Return value:

Empty table sequence

Example:

Generate an empty table sequence from an average record:

 

A

 

1

=demo.query("select top 1 * from DEPARTMENT")

2

=A1(1).create()

 

Create an empty table of same structure as A1(1) .

Generate an empty table sequence from a record with the key:

 

A

 

1

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

2

=A1.keys(DEPT)

 

3

=A1(1).create()

Generate an empty table sequence by copying the data structure of the record A1(1) and the key .