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:
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Fi |
Field name |
Return value:
An empty table sequence
Example:
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A |
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1 |
=create(id,name,gender) |
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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:
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Fi |
Field name |
Return value:
Empty table sequence
Example:
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A |
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1 |
=create(#id,#name,gender) |
id field and name field are keys |
f.create( C ,…; x )
Description:
Create a composite table based on a file.
f.create(C,…;x)
Note:
The function creates a composite table using composite table file f, and generates a multi-zone 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:
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f |
A composite table file or a homo-name files group |
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C |
A column of the would-be composite table |
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x |
A zone table expression |
Option:
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@u |
Do not compress the file; default is to compress it |
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@r |
Generate a row-wise file while default is columnar storage, which does not support the multicursor |
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@y |
Force to re-create the file even if the target file already exists; defalut is to terminate computation and report error |
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@p |
Use the first field as the grouping key |
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@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 |
Return value:
A composite table or a homo-name files group
Example:
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A |
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1 |
=file("employee1.ctx") |
Generate composite table file employee1.ctx |
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2 |
=A1.create(#EID,NAME,GENDER) |
Create A1’s base table whose columns are EID, NAME and GENDER; EID is the dimension |
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3 |
=connect("demo").cursor("select EID,NAME,GENDER,SALARY from employee where GENDER='M' order by SALARY") |
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4 |
=connect("demo").cursor("select EID,NAME,GENDER,SALARY from employee where GENDER='F' order by SALARY") |
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5 |
=[A3,A4].mcursor() |
Return a multicursor |
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6 |
=file("emp.ctx":[1,2]) |
Generate a homo-name files group, which contains two files 1.emp.ctx and 2.emp.ctx |
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7 |
=A6.create@y(#EID,NAME,GENDER,SALARY;if(GENDER=="F",1,2)) |
Create a multi-zone 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 |
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8 |
=A7.append@i(A5) |
Append data in A5’s multicursor to A7’s multi-zone composite table; each part of the multicursor uniquely corresponds to A7’s one zone table |
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9 |
=file("1.emp.ctx").open().cursor().fetch() |
View data in zone table 1.emp.ctx |
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10 |
=file("2.emp.ctx").open().cursor().fetch() |
View data in zone table 2.emp.ctx |
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A |
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1 |
=file("CITIES.ctx") |
Generate composite table file CITIES.ctx |
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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 |
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:
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P |
A record sequence |
Return value:
A new empty table sequence
Example:
Ø Generated from a record sequence
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A |
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1 |
=demo.query("select top 1 * from DEPARTMENT") |
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2 |
=A1.to() |
Generate a record sequence |
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3 |
=A2.create() |
Create an empty table sequence that has same data structure as A2’s |
Ø When there is the key
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A |
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1 |
=demo.query("select top 1 * from DEPARTMENT ") |
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2 |
=A1.keys(DEPT) |
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3 |
=A1.to() |
Generate a record sequence |
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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:
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T |
A table sequence |
Return value:
A new empty table sequence
Example:
Ø Created from a normal table sequence
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A |
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1 |
=demo.query("select top 1 * from DEPARTMENT") |
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2 |
=A1.create() |
Create an empty table of same structure as A1 |
Ø Copy the key
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A |
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1 |
=demo.query("select * from DEPARTMENT ") |
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2 |
=A1.keys(DEPT) |
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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;x )
Description:
Create a new composite table file using the data structure of an existing composite table.
Syntax:
T.create(f;x)
Note:
The function creates a new composite table file f using table structure of composite table T, and generates a multi-zone composite table file when the target f is a homo-name files group. f will include T’s attached tables.
Parameter:
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T |
A composite table |
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f |
A composite table file or a homo-name files group |
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x |
An integer, which is the zone table expression |
Return value:
A composite table
Example:
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A |
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1 |
=create(k1,v1).record([1,10,2,20]).cursor() |
Return a cursor that has data as follows:
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2 |
=create(k1,k2,v2).record([1,11,111,2,22,222]).cursor() |
Return a cursor that has data as follows:
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3 |
=file("ctb.ctx").open() |
Open a composite table file that contains an attached table table2 |
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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 |
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=A4.append@i(A1) |
Append data of A1’s cursor to the base table of composite table ctbCp.ctx |
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6 |
=A4.attach(table2) |
Open A4’s attached table table2 |
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7 |
=A6.append@i(A2) |
Append data of A2’s cursor to ctbCp.ctx’s attached table table2 |
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:
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r |
A record |
Return value:
A new empty table sequence
Example:
Ø Generate an empty table sequence from an average record
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A |
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1 |
=demo.query("select top 1 * from DEPARTMENT") |
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2 |
=A1(1).create() |
Create an empty table of same structure as A1(1) |
Ø Generate an empty table sequence from a record with the key
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A |
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1 |
=demo.query("select * from DEPARTMENT ") |
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2 |
=A1.keys(DEPT) |
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3 |
=A1(1).create() |
Generate an empty table sequence by copying the data structure of the record A1(1) and the key |