![]() A flat case expression does not have such an inherent precedence. On the other hand, nesting provides an inherent precedence among the conditions. This allows for multiple conditions even without nesting-unlike the ?: operator in other programming languages. is an arbitrary SQL expression: it can be a simple expression like a constant or column name, or also a complex SQL expression containing subqueries and, of course, nested case expressions.Ī case expression can contain several when- then pairs. Note that is a condition like those in where clauses-for example: column_name IS NULL. From that point of view, one could say that searched case is the only case syntax you absolutely need to remember. Furthermore searched case works in virtually all SQL databases. The other variants are abbreviations that could also be written as searched case. The following example shows the syntax in the most generic form-the so-called searched case. The syntax of the case expression is very flexible and allows for some abbreviations. ![]() ![]() Its use is similar to the ternary operator ?: in other programming languages. Being an expression-rather than a control structure-means that case varies the result of formulas (expressions) based on conditions. Nevertheless, SQL has something similar: the case expression. SQL is a declarative language: it does not provide control over program flow like if does for imperative programs.
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