Syntax Validation of the SQL Conditional Expression Based on Postfix-Expression Evaluation

The SQL conditional expression is not a constant expression, making it impossible to judge its legitimacy through the final value. However, there exists one alternative way where the elements in expression should be identified first to obtain the corresponding postfix data type expression, and the algorithms of SQL data types should be set to evaluate the postfix expression, then we can judge the syntactic legitimacy of the conditional expression in accordance with the final results. Tests conducted in this research have proved that this method can effectively validate the legitimacy of the SQL conditional expression and significantly serve for custom query and data analysis patterns.