Appendix A – Error Messages π«
Handling SQL text involves a series of steps. If a problem arises during any step, an error message appears, and the process terminates. π
Phases:
- Splitting into Keywords π: This step breaks down the SQL text into keywords, field names, and other elements. If an issue arises, an error message starting with "error parsing query:" is displayed. Potential errors include:
- Invalid character at the start of a token. ❌
- Invalid character after field separator. ⚠️
- Handling and Splitting Clauses ➗: The SQL text is divided into clauses separated by semi-colons. The clauses are then numbered for easier error identification. Errors in this phase include:
- Repeated use of a keyword within a clause. π
- Incorrect combination of keywords. ❎
- Improper ordering of sub-clauses. π
- Invalid table names after specific keywords. π«
- Incorrect syntax in SET clause. ⛔
- List Clauses π: Errors related to defining list clauses include:
- Duplicate variable definition. π
- Invalid list format. ❌
- Mismatch in data types within a list. ⚠️
- Unrecognized date format in a list. π
- Scalar Assignments π: Errors during scalar assignments involve:
- Duplicate variable definition. π
- Unrecognized date format. π
- Excessive length of LET clause. ❎
- Invalid data type assignment to scalar variables. ⚠️
- Handling Individual Clauses π§: During this phase, errors are reported with the clause number and the sub-clause name for clarity. Errors include:
- Misplacement of equal sign. ❌
- Unexpected comma. ⚠️
- Incorrect bracket usage. π«
- Invalid function names or parameters. ❎
- Improper use of aggregate functions. ⛔
- Incorrect use of the AS keyword. π«
- Checking Validity of Variable and Field Names ✅: Errors in this phase concern the validity of variable and field names. They include:
- Unrecognized field names. ❌
- Improper use of the asterisk (*). ⚠️
- Misuse of list variables. π
- Undefined variables. ❓
- Mismatch in variable usage context. ⛔
- Unrecognized date format. π
Additional Notes π:
- Forgetting the dollar sign in variable names in a LIST clause will produce an error. π²❌
- If a query only defines list variables, a message indicating no actions will be taken is shown. π«
Copyright: Wallingford Software 2010 ππ