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A case statement is a part of the MySQL documentation that is used to validate the SQL statements in the database server processes. In simple terms, a case statement is where you can assign conditions to each SQL statement being processed by the server. This helps the database system verifies whether or not each statement it processes is valid or whether a statement could have been misinterpreted. With case statements enabled, MySQL can tell if the intended actions of a client are actually what it was intended for.
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The main point to understand about a case statement is that the “case” part of the expression is optional. If no condition is supplied to the statement, the statement is executed without validation. There are, however, several variables that need to be provided to perform a proper case analysis. In this article, we will discuss some of these variables.
The first variable that is commonly associated with a case statement is “StmtId”. This is the identifier that is usually assigned to each statement being handled by the server. The station can be set at runtime, or it can be set when the statement is being processed.
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Another variable that is commonly used is “Condition”. This variable is used in conjunction with the StmtId to define the conditions the statement should pass through. Here is an example:
Let’s say that our character had a wish of not being put into jail. In such a case, our character would have selected the condition “He is not in jail”. In this case, we have defined two conditions: that the statement is put through as if it were set by the “rights” feature and that the value of the condition is “is not in jail”. To make the SQL statement more readable, we also wrote a check statement in which we provided the expression “hasRights” before the “if” statement. This way, we can easily view the result set.
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As we can see, the statement “rights” is used for two purposes: to determine if the condition is met, and then to evaluate the condition once the condition is met. In the following, we will examine how to build a case statement that does not pass through those two conditions. Once again, we will use the station. However, here, the station is optional, and the station is available on the value of the ExpressionParam table.
So, now you know how to create a case statement in MySQL. When building a case statement, we often prefer to use the station as the value for “Condition”. To do this, we simply use the StmtId as the Value of the ExpressionParam table for the Condition.
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