| Goal | This query identifies redundant null-handling logic within string manipulation expressions. It targets the use of explicit coalesce() calls nested inside functions that are already null-safe, such as concat(), concat_ws(), or format(). Since these functions implicitly treat NULL arguments as empty strings (or ignore them), wrapping arguments in coalesce(arg, '') is superfluous. The query deliberately excludes expressions using the standard concatenation operator (||), as coalesce() is legitimately required in that context to prevent null propagation. |
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| Type | Problem detection Each row in the result could represent a flaw in the design |
| Reliability | Low Many false-positive results |
| License | MIT (opens in new tab) |
| Fixing Suggestion | Do not use concat(coalesce(column1,''), ' ', coalesce(column2,'')) because concat treats NULL as empty string. Instead you can just use concat(column1, ' ', column2). |
| Data Source | INFORMATION_SCHEMA+system catalog |
| SQL Query |
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Collections
This query belongs to the following collections:
Find problems automatically
Queries, that results point to problems in the database. Each query in the collection produces an initial assessment. However, a human reviewer has the final say as to whether there is a problem or not .
| Name | Description |
|---|---|
| Find problems automatically | Queries, that results point to problems in the database. Each query in the collection produces an initial assessment. However, a human reviewer has the final say as to whether there is a problem or not . |
Categories
This query is classified under the following categories:
Derived tables
Queries of this category provide information about the derived tables (views, materialized views), which are used to implement virtual data layer.
Does not work in some earlier PostgreSQL version
Queries of this category provide information that was not available in some earlier PostgreSQL version
Missing data
Queries of this category provide information about missing data (NULLs) in a database.
System-defined functions
Queries of this category provide information about the use of system-defined functions.
User-defined routines
Queries of this category provide information about the user-defined routines
| Name | Description |
|---|---|
| Derived tables | Queries of this category provide information about the derived tables (views, materialized views), which are used to implement virtual data layer. |
| Does not work in some earlier PostgreSQL version | Queries of this category provide information that was not available in some earlier PostgreSQL version |
| Missing data | Queries of this category provide information about missing data (NULLs) in a database. |
| System-defined functions | Queries of this category provide information about the use of system-defined functions. |
| User-defined routines | Queries of this category provide information about the user-defined routines |