join()

Fi

Field name of the resulting table sequence

Ai

Sequences or record sequences to be joined

xj

Join field/ expression

@f

Full join; if no matching records are found, then use nulls to correspond

@1

Left join; it is the number "1" instead of the letter "l"

@m

If all A_i are ordered against x_j, then use merge operation to compute

@p

Perform a join according to positions while ignoring parameter xj

@i

Used only to filter A₁ and ignore parameter F_i; do not work with @f@1 options

@d

Used only to filter A₁ to retain records that cannot be found and ignore parameter F_i; do not work with @f@1 options

A

1

=demo.query("select top 3 EID,NAME from EMPLOYEE").keys(EID)

2

=demo.query("select top 3 EID,NAME from FAMILY").keys(EID)

3

=join(A1:Employee,EID;A2:Familymembers,EID)

A normal join that discards non-matching items; every field is a ref field pointing to the corresponding record in the original table sequence.

4

=join@f(A1:Employee,EID;A2:Familymembers,EID)

A full join that uses nulls to represent non-matching records.

5

=join@1(A1:Employee,EID;A2:Familymembers,EID)

A left join that uses the first table sequence as the basis and that uses nulls to correspond when no matching records can be found.

6

=join@m(A1:Employee,EID;A2:Familymembers,EID)

If all the join fields are in the same order, then merge operation can be used to compute; if they are not in the same order, then error will occur.

7

=join@p(A1:Employee;A2:Familymembers)

8

=join(A1:Employee;A2:Familymembers)

9

=join(A1:Employee1;A2:Familymembers1)

10

=join(A8:Employee2;A9:Familymembers2)

11

=join@i(A1;A2)

Filter A1 to retain records that can be found.

12

=join@d(A1;A2)

Filter A1 to retain records that cannot be found.

@i

Delete a record with a non-matching foreign key value; by default, a non-matching record will be represented by null. If parameters x:F are omitted, perform the filtering purely over parameter P

@d

If parameters x:F are absent, delete records matching the foreign key and perform the filtering operation only over table sequence/record sequence P

@m

Enable a merge join when P is ordered by C and T is ordered by K

P

Table sequence/record sequence

C

P’s foreign key; separate multiple fields in a composite key with the colon

T

Table sequence/record sequence

K

T’s key

x

T’s field expression, which can be represented by ~ and #; the pound sign # represents the sequence number of a record in T; record the sequence number as null if a record doesn’t exist in T

F

Field name in expression x

A

1

=connect("demo").query("SELECT * FROM CITIES")

Data of CITIES table:

2

=connect("demo").query("SELECT * FROM STATECAPITAL where STATEID<30").keys(STATEID)

Data of STATECAPITAL table:

3

=A1.join(STATEID,A2,CAPITAL)

Associate CITIES table and STATECAPITAL table through the foreign key, during which default parameter K is STATEID, the key of STATECAPTITAL, and add STATECAPITAL’s CAPITAL field to CITIES to generate a new table sequence.

4

=A1.join(STATEID,A2:#,CAPITAL)

As STATEID field values are natural numbers starting from 1, which correspond to sequence numbers of records in STATECPATITAL table, parameter K is written as # to use those sequence numbers in order to increae efficiency; return same result as A3.

5

=A1.join@i(STATEID,A2,CAPITAL)

@i option enables deleting records with non-matching foreign key values; write them as nulls if there isn’t the option.

6

=A1.join@i(STATEID,A2)

@i option enables filtering CITIES table only when parameters x:F are absent.

7

=A1.join@d(STATEID,A2)

With @d option and when parameters x:F are absent, delete records where foreign key values are matching and perform filtering only on CITIES table.

8

=A1.join(STATEID,A2,abc)

Write records where values of parameter x cannot be found in A2 as nulls.

9

=A1.join(STATEID,A2,CAPITAL:NAME)

Modify the existing fields when NAME field already exists in CITIES table.

A

1

=connect("demo").query("SELECT * FROM CITIES").sort(STATEID)

Below is data of CITIES table:

2

=connect("demo").query("SELECT * FROM STATECAPITAL where STATEID<30").keys(STATEID).sort(STATEID)

Below is data of STATECAPITAL table:

3

=A1.join@m(STATEID,A2,CAPITAL)

As CITIES table is ordered by STATEID and STATECAPITAL table is ordered by parameter K and with @m option being present, we can use MERGE method to compute.

@i

Delete the whole record if the foreign key can’t be matched; by default, make it null

@o(Fi; C:.,T:K,x:F,…; …;…)

Generate a new record by using the original record as a new field

@d

Delete the whole record matching foreign key value when parameters x:F are absent and perform filtering on ch only

@m

Use MERGE method during parallel computation when ch is ordered by the foreign key and T is ordered by its key

ch

A channel

C

Foreign key of a given channel; use comma to separate a composite key

T

A table sequence/record sequence

K

Key of the given table sequence/record sequence

x

A field expression of the given table sequence/record sequence

F

Name of the field expression

A

B

C

1

=connect("demo").cursor("SELECT top 10 CID,NAME,POPULATION,STATEID FROM CITIES")

A1 returns a cursor.

2

=connect("demo").query("SELECT top 40 * FROM STATECAPITAL").keys(STATEID)

A2 returns a table sequence using STATEID as the key:

3

=channel()

=A3.join(STATEID,A2,CAPITAL)

=B3.fetch()

A3 creates a channel;

B3 attaches a computation to channel A3, which will perform a foreign-key-style association between CITIES table and STATECAPITAL table, whose key, which is STATEID, is specified by parameter K by default, and join STATECAPITAL table’s field CAPITAL to the channel, and returns result to channel A3.

C3 executes the result set function in channel A2 and keeps the current data in channel.

4

=channel()

=A4.join(STATEID,A2:#,CAPITAL)

=B4.fetch()

A4 creates a channel;

B4 attaches a computation to channel A4 and returns result to channel A4. STATEID field values are natural numbers starting from 1, which correspond to record numbers in STATECAPITAL table; so parameter K can be specified as # to use those record numbers, which helps increase computing efficiency.

C4 executes the result set function in channel A2 and keeps the current data in channel.

5

=channel()

=A5.join@i(STATEID,A2,CAPITAL)

=B5.fetch()

A5 creates a channel;

B5 attaches a computation to channel A5, which will use @i option to delete the whole record in the channel if its foreign key cannot find a match – record the record as null by default – and returns result to channel A5.

C5 executes the result set function in channel A2 and keeps the current data in channel.

6

=channel()

=A6.join@d(STATEID,A2)

=B6.fetch()

A6 creates a channel;

B6 attaches a computation to channel A6, which will perform a filtering operation only on table CITIES and use @d option to delete the whole record in the channel if its foreign key finds a match when parameters x:F are absent, and returns result to channel A6.

C6 executes the result set function in channel A2 and keeps the current data in channel.

7

=channel()

=A7.join@o(cities;STATEID,A2,CAPITAL)

=B7.fetch()

A7 creates a channel;

B7 attaches a computation to channel A7, which will use @o option to generate new records using the original records of the channel as field cities, and returns result to channel A7.

C7 executes the result set function in channel A2 and keeps the current data in channel.

8

=A1.push(A3,A4,A5,A6,A7)

Be ready to push cursor A1’s data to channels A3, A4, A5, A6 and A7, but the action needs to wait.

9

=A1.fetch()

Fetch data from cursor A1 while pushing data to the channels to execute the attached computations and keep the results. Below is the returned result:

10

=A3.result()

Get channel A3’s result:

11

=A4.result()

Get channel A4’s result:

12

=A5.result()

Get channel A5’s result:

13

=A6.result()

Get channel A6’s result:

14

=A7.result()

Get channel A7’s result:

cs

A cursor/A multicursor

C

Cursor cs’s foreign key; separate multiple fields in a composite key with the colon

T

A table sequence/A record sequence

K

T’s key

x

T’s field expression

F

Field name in expression x.

@i

Delete a record with a non-matching foreign key value; by default, a non-matching record will be represented by null

@o(F_i; C:.,T:K,x:F,…; …;…)

Use the original record as the value of F_i field to generate a new record

@d

If parameters x:F are absent, only perform a filtering over the cursor by deleting its records where the foreign key is matched

@m

Enable a merge join when cs is ordered by C and T is ordered by K

A

1

=connect("demo").cursor("SELECT top 10 CID,NAME,POPULATION,STATEID FROM CITIES")

Return a cursor, whose data is as follows:

2

=connect("demo").query("SELECT top 40 * FROM STATECAPITAL").keys(STATEID)

Return a table sequence whose key is STATEID:

3

=A1.join(STATEID,A2,CAPITAL)

Attach a computation to cursor A1, which creates association between CITIES table and STATECAPITAL table through the foreign key specified by parameter K, whose value is by default the latter’s key, STATEID, and adds field CAPITAL in STATECAPITAL to the cursor, and return the original cursor.

4

=A1.fetch()

Fetch data from cursor A1 where A3’s computation is executed (it would be better to fetch data in batches when there is a huge amount of data):

A

1

=connect("demo").cursor("SELECT top 10 CID,NAME,POPULATION,STATEID FROM CITIES")

Return a cursor whose data is as follows:

2

=connect("demo").query("SELECT top 40 * FROM STATECAPITAL").keys(STATEID)

Return a table sequence whose key is STATEID:

3

=A1.join(STATEID,A2:#,CAPITAL)

Attach a computation to cursor A1 and return the original cursor; as STATEID field values are natural numbers beginning from 1 that strictly correspond to record numbers in STATECAPITAL table, we can write parameter K as #, which means sequence numbers in the table can be directly used to increase the computing efficiency.

4

=A1.fetch()

Fetch data from cursor A1 where A3’s computation is executed:

A

1

=connect("demo").cursor("SELECT top 10 CID,NAME,POPULATION,STATEID FROM CITIES")

Return a cursor whose data is as follows:

2

=connect("demo").query("SELECT top 40 * FROM STATECAPITAL").keys(STATEID)

Return a table sequence whose key is STATEID:

3

=A1.join@i(STATEID,A2,CAPITAL)

Attach a computation to cursor A1, which, with @i option, deletes the whole record from the cursor if the foreign key does not match – by default the corresponding value is recorded as null, and return the original cursor.

4

=A1.fetch()

Fetch data from cursor A1 where A3’s computation is executed:

A

1

=connect("demo").cursor("SELECT top 10 CID,NAME,POPULATION,STATEID FROM CITIES")

Return a cursor whose data is as follows:

2

=connect("demo").query("SELECT top 40 * FROM STATECAPITAL").keys(STATEID)

Return a table sequence whose key is STATEID:

3

=A1.join@i(STATEID,A2)

Attach a computation to cursor A1, which, with @i option, performs a filtering operation only on CITIES table when parameters x:F are absent , and return the original cursor.

4

=A1.fetch()

Fetch data from cursor A1 where A3’s computation is executed:

A

1

=connect("demo").cursor("SELECT top 10 CID,NAME,POPULATION,STATEID FROM CITIES")

Return a cursor whose data is as follows:

2

=connect("demo").query("SELECT top 40 * FROM STATECAPITAL").keys(STATEID)

Return a table sequence whose key is STATEID:

3

=A1.join@d(STATEID,A2)

Attach a computation to cursor A1, which, with @d option, deletes the whole record in the cursor that matches the foreign key when parameters x:F are absent to achieve a filtering operation on CITIES table, and return the original cursor.

4

=A1.fetch()

Fetch data from cursor A1 where A3’s computation is executed:

A

1

=connect("demo").cursor("SELECT top 10 CID,NAME,POPULATION,STATEID FROM CITIES")

Return a cursor whose data is as follows:

2

=connect("demo").query("SELECT top 40 * FROM STATECAPITAL").keys(STATEID)

Return a table sequence whose key is STATEID:

3

=A1.join(STATEID,A2,abc)

Attach a computaton to cursor A1, which records the corresponding field as null if parameter x value does not exist in A2, and return the original cursor.

4

=A1.fetch()

Fetch data from cursor A1 where A3’s computation is executed:

A

1

=connect("demo").cursor("SELECT top 10 CID,NAME,POPULATION,STATEID FROM CITIES")

Return a cursor whose data is as follows:

2

=connect("demo").query("SELECT top 40 * FROM STATECAPITAL").keys(STATEID)

Return a table sequence whose key is STATEID:

3

=A1.join@o(cities;STATEID,A2,CAPITAL)

Attach a computation to cursor A1, which, with @o option, generates new records by making the cursor’s records values of cities field, and return the original A1.

4

=A1.fetch()

Fetch data from cursor A1 where A3’s computation is executed:

A

1

=connect("demo").cursor("SELECT top 10 CID,NAME,POPULATION,STATEID FROM CITIES")

Return a cursor whose data is as follows:

2

=connect("demo").query("SELECT top 40 * FROM STATECAPITAL").keys(STATEID)

Return a table sequence whose key is STATEID:

3

=A1.join(STATEID,A2,CAPITAL:NAME)

Attach a computation to cursor A1, which modifies the existing field as NAME field already exists in CITIES table, and return the original cursor.

4

=A1.fetch()

Fetch data from cursor A1 where A3’s computation is executed:

@c

With a distributed cluster table, the operation won’t involve a cross-node reference but it assumes that the referenced records are local

cs

A cursor/multicursor/cluster cursor

C

cs’s foreign key; separate multiple fields in a composite key with the colon

T

A cluster in-memory table

K

T’s key

x

T’s field expression

F

Name of T’s field expression

A

1

[192.168.18.143:8281]

2

=file("emp_1.ctx":[2], A1)

3

=A2.open()

4

=A3.cursor()

A cluster cursor.

5

[192.168.0.110:8281]

6

=file("PERFORMANCE.ctx":[1],A5)

7

=A6. open ()

8

=A7.cursor()

9

=A8.memory()

A cluster in-memory table.

10

=A4.join(EID,A9:EMPLOYEEID, BONUS*12:total)

Match EID field of A4’s cluster cursor with the key field EMPLOYEEID of A9’s cluster in-memory table, make the value of calculating expression BONUS*12 over the memory table’s total field and join it up with the cluster cursor, and return the cluster cursor.

11

=A10.fetch()

Fetch data from A10’s cursor.

@i

Delete a record with a non-matching foreign key value; by default, a non-matching record will be represented by null

@o(Fi; C:.,T:K,x:F,…; …;…)

Use the record as the value of F field to generate a new record

@d

When parameters x:F are absent, delete whole records matching the foreign key and perform the filtering operation only over pseudo table T

@m

Enable a merge join when T is ordered by C and A is ordered by K

T

A pseudo table

C

T’s foreign key; separate multiple fields in a composite key with the colon

A

Table sequence/record sequence

K

A’s key

x

A’s field expression

F

Field name in expression x

A

B

1

=create(file).record(["cities.ctx"])

Below is content of composite table cities.ctx:

2

=pseudo(A1)

Generate a pseudo table from the composite table.

3

=connect("demo").query("SELECT * FROM STATECAPITAL where STATEID<30").keys(STATEID)

Below is content of STATECAPITAL:

4

=A2.join(STATEID,A3,CAPITAL)

=A4.cursor().fetch()

Execute expression in A4. Define a computation on A2’s pseudo table, which will associate A2’s pseudo table CITIES and A3’s STATECAPITAL table through the foreign key, during which default parameter K is STATEID, the key of STATECAPTITAL, and add STATECAPITAL’s CAPITAL field to CITIES to generate a new pseudo table.

Execute expression in B4: fetch data from A4’s pseudo table while executing the computation defined in A4 on A2’s pseudo table, and return the following table:

5

=A2.join(STATEID,A3:#,CAPITAL)

=A5.import()

Execute expression in A5. Define a computation on A2’s pseudo table; as STATEID field values are natural numbers starting from 1, which correspond to ordinarl numbers of records in STATECPATITAL table, parameter K is written as # to use those sequence numbers in order to increae efficiency;

Execute expression in B5 and return same result as B4.

6

=A2.join@i(STATEID,A3,CAPITAL)

=A6.import()

@i option enables deleting records with non-matching foreign key values – write them as nulls if there isn’t the option – and execute B6 and return the following table:

7

=A2.join@i(STATEID,A3)

=A7.import()

@i option enables filtering CITIES table only when parameters x:F are absent; execute B7 and return the following table:

8

=A2.join@d(STATEID,A3)

=A8.import()

With @d option and when parameters x:F are absent, delete records where foreign key values are matching and perform filtering only on pseduo table CITIES; execute B8 and return the following table:

9

=A2.join(STATEID,A3,abc)

=A9.import()

Write records where values of parameter x cannot be found in A2 as nulls; execute B9 and return the following table:

10

=A2.join@o(cities;STATEID,A3,CAPITAL)

=A10.import()

@o option enables to take the whole orignal record as a cities value to generate a new record; this is equivalent to an expression where parameter x is ~; execute B10 and return the following table:

11

=A2.join(STATEID,A3,CAPITAL:NAME)

=A11.import()

Modify the existing fields when NAME field already exists in CITIES table; execute B11 and return the following table: