Database & JDBC

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title: "Database & JDBC" date: "2024-09-28" excerpt: "JDBC fundamentals: core interfaces, connection APIs, prepared/callable statements, bind variables, and ResultSet behavior."

tags: "java,jdbc,database" source: "https://shrikant-havale.in/2024/09/28/database-jdbc/"

A concise reference for JDBC basics and common interview/exam details.

JDBC Core Concepts

• JDBC drivers provide concrete implementations for each database vendor.
• Core interfaces live under java.sql:
  • Driver
  • Connection
  • PreparedStatement
  • CallableStatement
  • ResultSet

JDBC URL

JDBC URLs follow:

protocol:subprotocol:subname

• Protocol is always jdbc.
• Subprotocol is typically the database name.
• Subname format depends on vendor.

Connections

DriverManager.getConnection(...) throws checked SQLException.

DriverManager.getConnection("connection-string");
DriverManager.getConnection("connection-string", "username", "password");

Statements

• PreparedStatement extends Statement and supports bind parameters.
• CallableStatement extends Statement and is used for stored procedures.

PreparedStatement ps = conn.prepareStatement("update ...");
int updated = ps.executeUpdate();

PreparedStatement ps = conn.prepareStatement("select ...");
ResultSet rs = ps.executeQuery();

execute() returns a boolean:

• true => result is a ResultSet
• false => use update count

Bind Variables

• Indexing starts at 1 (not 0).
• Missing or extra bind variables cause SQLException.

ResultSet Safety

SQLException can occur when:

• Accessing a non-existing column name/index.
• Reading when cursor is not on a valid row.

Source

Original post: https://shrikant-havale.in/2024/09/28/database-jdbc/