Introduction

This project analyses SQL statements and labels possible errors or complications.

Credits

Special thanks to Davide Miggiano and Flavio Venturini for their valuable contributions to the development of this project.

Limitations

Fully identified schema names are not supported when specifying column names (e.g. SELECT schema.table.column [...])

SQL Errors TODO List

Syntax Errors

ID	Category	Name	Description	Base Query	Subquery	CTE
1	SYN-1	Ambiguous database object	Omitting correlation names	✓
2	SYN-1	Ambiguous database object	Ambiguous column	✓
3	SYN-1	Ambiguous database object	Ambiguous function
4	SYN-2	Undefined database object	Undefined column	✓	✓	✓
5	SYN-2	Undefined database object	Undefined function	✓	✓	✓
6	SYN-2	Undefined database object	Undefined parameter	✓	✓	✓
7	SYN-2	Undefined database object	Undefined object	✓	✓	✓
8	SYN-2	Undefined database object	Invalid schema name	✓
9	SYN-2	Undefined database object	Misspellings	✓
10	SYN-2	Undefined database object	Synonyms
11	SYN-2	Undefined database object	Omitting quotes around character data	✓	✓	✓
12	SYN-3	Data type mismatch	Failure to specify column name twice
13	SYN-3	Data type mismatch	Data type mismatch	✓
14	SYN-4	Illegal aggregate function placement	Using aggregate function outside SELECT or HAVING	✓	✓	✓
15	SYN-4	Illegal aggregate function placement	Grouping error: aggregate functions cannot be nested	✓	✓	✓
16	SYN-5	Illegal or insufficient grouping	Grouping error: extraneous or omitted grouping column	✓	✓	✓
17	SYN-5	Illegal or insufficient grouping	Strange HAVING: HAVING without GROUP BY	✓	✓	✓
18	SYN-6	Common syntax error	Confusing function with function
19	SYN-6	Common syntax error	Using WHERE twice	✓	✓	✓
20	SYN-6	Common syntax error	Omitting the FROM clause	✓	✓	✓
21	SYN-6	Common syntax error	Comparison with NULL	✓	✓	✓
22	SYN-6	Common syntax error	Omitting the semicolon	✓	✓	✓
23	SYN-6	Common syntax error	Date time field overflow
24	SYN-6	Common syntax error	Duplicate clause
25	SYN-6	Common syntax error	Using an undefined correlation name
26	SYN-6	Common syntax error	Too many columns in subquery
27	SYN-6	Common syntax error	Confusing table names with column names
28	SYN-6	Common syntax error	Restriction in SELECT clause (e.g., SELECT fee > 10)	✓	✓	✓
29	SYN-6	Common syntax error	Projection in WHERE clause (e.g., WHERE firstname, surname)	✓	✓	✓
30	SYN-6	Common syntax error	Confusing the order of keywords (e.g., FROM customer SELECT fee)	✓
31	SYN-6	Common syntax error	Confusing the logic of keywords (e.g., grouping instead of ordering)
32	SYN-6	Common syntax error	Confusing the syntax of keywords (e.g., LIKE (‘A’, ‘B’))	✓	✓	✓
33	SYN-6	Common syntax error	Omitting commas	✓	✓	✓
34	SYN-6	Common syntax error	Curly, square or unmatched brackets	✓	✓	✓
35	SYN-6	Common syntax error	IS where not applicable
36	SYN-6	Common syntax error	Nonstandard keywords or standard keywords in wrong context
37	SYN-6	Common syntax error	Nonstandard operators (e.g., &&, \|\| or ==)	✓	✓	✓
38	SYN-6	Common syntax error	Additional semicolon	✓	✓	✓

Semantic Errors

ID	Category	Name	Description	Base Query	Subquery	CTE
39	SEM-1	Inconsistent expression	AND instead of OR (empty result table)	✓
40	SEM-1	Inconsistent expression	Implied, tautological or inconsistent expression
41	SEM-1	Inconsistent expression	DISTINCT in SUM or AVG	✓	✓	✓
42	SEM-1	Inconsistent expression	DISTINCT that might remove important duplicates
43	SEM-1	Inconsistent expression	Wildcards without LIKE	✓	✓	✓
44	SEM-1	Inconsistent expression	Incorrect wildcard: using _ instead of % or using, e.g., *	✓	✓	✓
45	SEM-1	Inconsistent expression	Mixing a > 0 with IS NOT NULL or empty string with NULL	✓	✓	✓
46	SEM-2	Inconsistent join	NULL in IN/ANY/ALL subquery
47	SEM-2	Inconsistent join	Join on incorrect column (matches impossible)
48	SEM-3	Missing join	Omitting a join
49	SEM-4	Duplicate rows	Many duplicates
50	SEM-5	Redundant column output	Constant column output	✓
51	SEM-5	Redundant column output	Duplicate column output	✓

Logical Errors

ID	Category	Name	Description	Base Query	Subquery	CTE
52	LOG-1	Operator error	OR instead of AND	✓	✓	✓
53	LOG-1	Operator error	Extraneous NOT operator
54	LOG-1	Operator error	Missing NOT operator
55	LOG-1	Operator error	Substituting existence negation with <>
56	LOG-1	Operator error	Putting NOT in front of incorrect IN/EXISTS
57	LOG-1	Operator error	Incorrect comparison operator or incorrect value compared	✓	✓	✓
58	LOG-2	Join error	Join on incorrect table
59	LOG-2	Join error	Join when join needs to be omitted
60	LOG-2	Join error	Join on incorrect column (matches possible)
61	LOG-2	Join error	Join with incorrect comparison operator
62	LOG-2	Join error	Missing join
63	LOG-3	Nesting error	Improper nesting of expressions
64	LOG-3	Nesting error	Improper nesting of subqueries
65	LOG-4	Expression error	Extraneous quotes
66	LOG-4	Expression error	Missing expression	✓	✓	✓
67	LOG-4	Expression error	Expression on incorrect column	✓	✓	✓
68	LOG-4	Expression error	Extraneous expression	✓	✓	✓
69	LOG-4	Expression error	Expression in incorrect clause
70	LOG-5	Projection error	Extraneous column in SELECT	✓	✓	✓
71	LOG-5	Projection error	Missing column from SELECT	✓	✓	✓
72	LOG-5	Projection error	Missing DISTINCT from SELECT
73	LOG-5	Projection error	Missing AS from SELECT
74	LOG-5	Projection error	Missing column from ORDER BY clause	✓
75	LOG-5	Projection error	Incorrect column in ORDER BY clause	✓
76	LOG-5	Projection error	Extraneous ORDER BY clause	✓
77	LOG-5	Projection error	Incorrect ordering of rows	✓
78	LOG-6	Function error	DISTINCT as function parameter where not applicable
79	LOG-6	Function error	Missing DISTINCT from function parameter
80	LOG-6	Function error	Incorrect function
81	LOG-6	Function error	Incorrect column as function parameter

Complications

ID	Category	Name	Description	Base Query	Subquery	CTE
82	COM	Complication	Unnecessary complication
83	COM	Complication	Unnecessary DISTINCT in SELECT clause	✓	✓	✓
84	COM	Complication	Unnecessary join	✓
85	COM	Complication	Unused correlation name
86	COM	Complication	Correlation names are always identical
87	COM	Complication	Unnecessarily general comparison operator
88	COM	Complication	LIKE without wildcards	✓	✓	✓
89	COM	Complication	Unnecessarily complicated SELECT in EXISTS subquery
90	COM	Complication	IN/EXISTS can be replaced by comparison
91	COM	Complication	Unnecessary aggregate function
92	COM	Complication	Unnecessary DISTINCT in aggregate function
93	COM	Complication	Unnecessary argument of COUNT
94	COM	Complication	Unnecessary GROUP BY in EXISTS subquery
95	COM	Complication	GROUP BY with singleton groups
96	COM	Complication	GROUP BY with only a single group
97	COM	Complication	GROUP BY can be replaced with DISTINCT
98	COM	Complication	UNION can be replaced by OR
99	COM	Complication	Unnecessary column in ORDER BY clause	✓
100	COM	Complication	ORDER BY in subquery
101	COM	Complication	Inefficient HAVING
102	COM	Complication	Inefficient UNION
103	COM	Complication	Condition in the subquery can be moved up
104	COM	Complication	Condition on left table in LEFT OUTER JOIN
105	COM	Complication	OUTER JOIN can be replaced by INNER JOIN

License
- OSI Approved :: MIT License
Operating System
- OS Independent
Programming Language
- Python :: 3

Metadata

License
- OSI Approved :: MIT License
Operating System
- OS Independent
Programming Language
- Python :: 3

Release files for sqlchecker 1.0.1

For a detailed explanation of source distributions (sdists) and built distributions (wheels), please see the package formats documentation.

Source distribution (sdist)

Source distribution for sqlchecker 1.0.1
File	Size	Uploaded
sqlchecker-1.0.1.tar.gz	128.7 kB	Oct 7, 2026	Details

Built distribution (wheel)

Table of built distributions (wheels) for sqlchecker 1.0.1
File	Interpreter	ABI	Platform	Reset
sqlchecker-1.0.1-py3-none-any.whl 33.9 kB Oct 7, 2026	Python 3	none	any	Details

Total release size: 162.6 kB

Release files / sqlchecker-1.0.1.tar.gz

Download URL	sqlchecker-1.0.1.tar.gz
Size	128.7 kB
Tags	Source
SHA-256 checksum How to use checksums	`0410709350fb593d44f385bc48455ebd66f9b4083482cba746579dab6a9650a6`
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Uploaded via	`twine/7.0.0 CPython/3.12.3`

Release files / sqlchecker-1.0.1-py3-none-any.whl

Download URL	sqlchecker-1.0.1-py3-none-any.whl
Size	33.9 kB
Tags	Python 3
SHA-256 checksum How to use checksums	`e3638866b5cd44b40b542d0197c5bccd0d843a2b5df195fa99d93dceb5c51743`
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Upload date	Oct 7, 2026
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Uploaded via	`twine/7.0.0 CPython/3.12.3`