Maintaining cardinality of rows while joining worksheets from a database

1. A method of maintaining cardinality of rows while joining worksheets from a database, the method comprising:

receiving, by a joining module from a client computing system, a request to join, to a first worksheet, a second worksheet from the database on a cloud-based data warehouse, wherein the request comprises a join key;

generating, by the joining module, a first database statement to create a group of join rows in the database that each correspond to a row in the first worksheet based on the join key;

sending, by the joining module, the generated first database statement to the cloud-based data warehouse;

retrieving, by the joining module using a second database statement, the group of join rows from the cloud-based data warehouse; and

presenting, on the client computing system by the joining module, each of the group of join rows adjacent to a corresponding row in the first worksheet.

2. The method of claim 1 , wherein generating the first database statement to create the group of join rows in the database comprises:

for each row in the first worksheet:

generating a join row for data from the second worksheet; and

in response to determining that there is at least one matching row in the second worksheet on the database:

compare, by the joining module, a maximum value and a minimum value for each column in each row of the at least one matching row;

if the maximum value and the minimum value match, store, by the joining module, a matching value in a corresponding column of the join row on the database; and

if the maximum value and the minimum value do not match, store, by the joining module, a multiple value indication in the corresponding column of the join row on the database.

3. The method of claim 2 , wherein generating the first database statement to create the group of join rows in the database further comprises:

in response to determining that there is no matching row in the second worksheet, store a null value in each column of the join row.

4. The method of claim 2 , wherein at least one of the maximum value and the minimum value for at least one column comprises a null value.

5. The method of claim 2 , wherein the multiple value indication communicates a number of different values in the corresponding column.

6. An apparatus for maintaining cardinality of rows while joining worksheets from a database, the apparatus comprising a computer processor, a computer memory operatively coupled to the computer processor, the computer memory having disposed within it computer program instructions that, when executed by the computer processor, cause the apparatus to carry out the steps of:

receiving, by a joining module from a client computing system, a request to join, to a first worksheet, a second worksheet from the database on a cloud-based data warehouse, wherein the request comprises a join key;

generating, by the joining module, a first database statement to create a group of join rows in the database that each correspond to a row in the first worksheet based on the join key;

sending, by the joining module, the generated first database statement to the cloud-based data warehouse;

retrieving, by the joining module using a second database statement, the group of join rows from the cloud-based data warehouse; and

presenting, on the client computing system by the joining module, each of the group of join rows adjacent to a corresponding row in the first worksheet.

7. The apparatus of claim 6 , wherein generating the first database statement to create the group of join rows in the database comprises:

for each row in the first worksheet:

generating a join row for data from the second worksheet; and

in response to determining that there is at least one matching row in the second worksheet on the database:

compare, by the joining module, a maximum value and a minimum value for each column in each row of the at least one matching row;

if the maximum value and the minimum value match, store, by the joining module, a matching value in a corresponding column of the join row on the database; and

if the maximum value and the minimum value do not match, store, by the joining module, a multiple value indication in the corresponding column of the join row on the database.

8. The apparatus of claim 7 , wherein generating the first database statement to create the group of join rows in the database further comprises:

in response to determining that there is no matching row in the second worksheet, store a null value in each column of the join row.

9. The apparatus of claim 7 , wherein at least one of the maximum value and the minimum value for at least one column comprises a null value.

10. The apparatus of claim 7 , wherein the multiple value indication communicates a number of different values in the corresponding column.

11. A computer program product for maintaining cardinality of rows while joining worksheets from a database, the computer program product disposed upon a non-transitory computer readable medium, the computer program product comprising computer program instructions that, when executed, cause a computer to carry out the steps of:

receiving, by a joining module from a client computing system, a request to join, to a first worksheet, a second worksheet from the database on a cloud-based data warehouse, wherein the request comprises a join key;

generating, by the joining module, a first database statement to create a group of join rows in the database that each correspond to a row in the first worksheet based on the join key;

sending, by the joining module, the generated first database statement to the cloud-based data warehouse;

retrieving, by the joining module using a second database statement, the group of join rows from the cloud-based data warehouse; and

presenting, on the client computing system by the joining module, each of the group of join rows adjacent to a corresponding row in the first worksheet.

12. The computer program product of claim 11 , wherein generating the first database statement to create the group of join rows in the database comprises:

for each row in the first worksheet:

generating a join row for data from the second worksheet; and

in response to determining that there is at least one matching row in the second worksheet on the database:

compare, by the joining module, a maximum value and a minimum value for each column in each row of the at least one matching row;

if the maximum value and the minimum value match, store, by the joining module, a matching value in a corresponding column of the join row on the database; and

if the maximum value and the minimum value do not match, store, by the joining module, a multiple value indication in the corresponding column of the join row on the database.

13. The computer program product of claim 12 , wherein generating the first database statement to create the group of join rows in the database further comprises:

in response to determining that there is no matching row in the second worksheet, store a null value in each column of the join row.

14. The computer program product of claim 12 , wherein at least one of the maximum value and the minimum value for at least one column comprises a null value.

15. The computer program product of claim 12 , wherein the multiple value indication communicates a number of different values in the corresponding column.