How to Concatenate One-to-Many Relationships into Unique Columns in Informix?

Concatenate One-to-Many Relationships as Unique Columns in Informix

Converting one-to-many relationships into two unique columns requires specific database functions and syntax. This question explores how to achieve this conversion using Informix SQL, similar to the approach described in the referenced StackOverflow questions.

User-Defined Aggregate Function

The proposed solution involves creating a user-defined aggregate function named group_concat. This function employs four sub-functions:

• gc_init: Initializes the empty string.
• gc_iter: Iteratively appends values to the string, separated by commas.
• gc_comb: Combines partial results generated from different partitions.
• gc_fini: Returns the final concatenated string.

Query for Concatenation

To concatenate the codes for each unique ID, execute the following query:

SELECT id, group_concat(codes)
FROM anonymous_table
GROUP BY id;

Example Table and Results

The example table anonymous_table contains duplicate codes for multiple IDs. The output of the query produces the desired result:

id    codes
63592 PELL
58640 SUBL, USBL
73571 PELL, USBL, SUBL

Notes

• The group_concat aggregate can handle any data type convertible to VARCHAR(255), such as numeric and temporal types.
• The aggregate size is limited to 2048 bytes by default (up to 16380 bytes in Informix 12.10.FC5), posing potential limitations for extensive data.
• To remove the aggregate function, use the provided drop commands.

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