Where is prepared statement compiled

If you later add an index, the compiled query cannot use the index because it didn't know about it at compile time. It is already translated into code the database server understands. Only placeholders are left for the variables you are inserting.

For example a Java program also has to be compiled from source code to byte-code, where the soruce code is the human readable for of the program and the bytecode is the representation if the source code which is also understood by the machine.

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Learn more. What does it mean when I say Prepared statement is pre-compiled? Ask Question. Asked 7 years, 5 months ago. Active 4 years, 3 months ago. Viewed 11k times. What do we mean by compiled? Improve this question. Lukas Kabrt 5, 4 4 gold badges 41 41 silver badges 58 58 bronze badges.

Add a comment. Active Oldest Votes. Other advantages of prepared statements are :- 1 protection against SQL-injection attack 2 Faster for successive calls of same statements How it works :- Precompilation is done by the database.

Databases generally cache statements until something evicts them from the cache. Improve this answer. Buhake Sindi 84k 27 27 gold badges silver badges bronze badges. No arguments are supplied to executeUpdate when they are used to execute updateSales and updateTotals ; both PreparedStatement objects already contain the SQL statement to be executed.

Note : At the beginning of CoffeesTable. Consequently, no SQL statements are committed until the method commit is called. For more information about the auto-commit mode, see Transactions. Whereas executeQuery returns a ResultSet object containing the results of the query sent to the DBMS, the return value for executeUpdate is an int value that indicates how many rows of a table were updated. For instance, the following code shows the return value of executeUpdate being assigned to the variable n :.

That update affects one row in the table, so n is equal to 1. When the method executeUpdate is used to execute a DDL data definition language statement, such as in creating a table, it returns the int value of 0. Note that when the return value for executeUpdate is 0, it can mean one of two things:. All rights reserved. Hide TOC.

JDBC Basics. Retrieving and Modifying Values from Result Sets. Subsequent executions can use the same statement execution plan even if the parameter values are different. PreparedStatements are not shared across connections. Remember: If your application executes statements that are almost but not exactly alike, it is more efficient to use PreparedStatements with dynamic or IN parameters.

Figure 2. A database can reuse a statement execution plan when the SQL text matches a prior statement exactly. PreparedStatements are much more efficient.