Brief explanation is needed, why the item is True of why it is false. True/False

Question

Brief explanation is needed, why the item is True of why it is false.

True/False - Circle the correct choice A) A SQL query is first written, then parsed, then optimized, and finally executed. True/False. B) For a given SQL query, there can only be one query plan. True/False. C) A trigger can be fired only when a new row is inserted into the DB. True/False D) When a view is created, all the data from the referenced table(s) is copied into a new table with the given view name. True/False. E) Database clients can use JDBC to access a database server to execute SQL queries. True/False

Explanation / Answer

A) TRUE

EXPLANATION: When an sql query is written, it is complied before execution

Compilation alone comes with 3 stages, which are, 1. parsing, 2. binding and 3. optimization.

Parsing is done to check the syntax , where the structure of the query is checked. Whether is is written correctly or not.

Binding is the process done by algebraizer. This is to check the semantics of the query is correct or not. For example. if we are trying to obtain the details of two tables into one table. Algebraizer checks, according to the query written, whether it exists or not.

Optimization, the last step in Compilation process generates the execution plan, with the most efficient way to execute it.

then the query is executed with the generated executeion plan.

B) FALSE

There is something called Nested queries exist. Where we can execute 2or more queries within a query.

C)TRUE

A trigger can be fired if inser delete or update event occurs. So tehcnically the statement is true

D)TRUE

Because view table is a virtual table. It will have the values from the referenced tables according to the query and with the name we specify for that view.

E) True

Jdbc is an application programming interface for JAVA language, which defines how a client can access data base server to get his queries.

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