SQL CLI – Multi‑database Command‑Line Client (Java)

A lightweight, single‑JAR SQL client you can run from the terminal. It connects to MySQL, Oracle, PostgreSQL, MariaDB, Microsoft SQL Server and db2 gives you an interactive prompt with auto‑completion, prints results in a pretty table (with correct width for wide characters like Korean), and adds safety prompts for destructive statements.

Built with Java 21, JLine 3, and the official JDBC drivers.

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Features

• Interactive REPL powered by JLine (multi‑line input, history, Ctrl+D to exit).
• Auto‑completion for table and column names using live database metadata.
• Pretty table output that aligns columns and accounts for double‑width characters.
• Safety checks that detect:
  • DELETE without WHERE
  • UPDATE without WHERE
  • DROP TABLE …and ask for confirmation before executing.
• Run scripts: execute a .sql file containing multiple statements separated by semicolons.
• Autocommit toggle: quickly switch autocommit on/off.
• Password prompt: omit --password to be securely prompted at runtime.

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Supported databases

DB	JDBC driver (pom)	Example JDBC URL
PostgreSQL	org.postgresql:postgresql:42.7.3	jdbc:postgresql://localhost:5432/mydb
MySQL	com.mysql:mysql-connector-j:9.0.0	jdbc:mysql://localhost:3306/mydb?useSSL=false
Oracle	com.oracle.database.jdbc:ojdbc11:23.4.0.24.05	jdbc:oracle:thin:@//localhost:1521/ORCLPDB1
SQL Server	com.microsoft.sqlserver:mssql-jdbc:12.6.1.jre11	jdbc:sqlserver://localhost:1433;databaseName=mydb

Note: You only need the driver for the database(s) you actually connect to. Maven downloads them automatically when you build.

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Requirements

• Java 21+
• Maven 3.9+ (to build the fat jar)

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Build

mvn -q -DskipTests package

The build produces a runnable JAR in target/. Depending on your Maven/shade settings it may be named:

• cli-db-tool-1.0-SNAPSHOT.jar, or
• cli-db-tool-1.0-SNAPSHOT-shaded.jar

Use whichever exists in target/.

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Quick start

1) PostgreSQL

java -jar target/cli-db-tool-1.0-SNAPSHOT.jar \
  --driver postgres \
  --url jdbc:postgresql://localhost:5432/mydb \
  --username myuser
# You will be prompted for the password if --password is omitted

2) MySQL

java -jar target/cli-db-tool-1.0-SNAPSHOT.jar \
  --driver mysql \
  --url "jdbc:mysql://localhost:3306/mydb?useSSL=false" \
  --username myuser --password secret

3) Oracle

java -jar target/cli-db-tool-1.0-SNAPSHOT.jar \
  --driver oracle \
  --url "jdbc:oracle:thin:@//localhost:1521/ORCLPDB1" \
  --username myuser

4) SQL Server

java -jar target/cli-db-tool-1.0-SNAPSHOT.jar \
  --driver mssql \
  --url "jdbc:sqlserver://localhost:1433;databaseName=mydb" \
  --username myuser

CLI options

• --driver (required): one of mysql, oracle, postgres, mssql, mariadb, db2
• --url (required): JDBC URL
• --username (required)
• --password (optional): if omitted you’ll be prompted securely

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Interactive commands

At the sql> prompt you can use:

Command	Description
help	Show a quick help/usage panel.
file <path.sql>	Execute SQL statements from a file (semicolon ; separated).
toggle autocommit	Toggle autocommit on/off (default: ON).
clear	Clear the screen.
exit	Exit the program (or press Ctrl+D).

Notes on scripts (file <path.sql>):

• Statements are split on the semicolon (;).
• A trailing statement without a final semicolon will still be executed.
• Complex vendor‑specific blocks (e.g., PL/SQL BEGIN … END;) may not be parsed as a single unit.

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Output formatting

• Results are printed as a fixed‑width table with a header and separators.
• Column widths adapt to the largest cell in each column.
• Double‑width characters (e.g., Korean) are handled correctly so columns stay aligned.

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Project structure

src/main/java/project/
├─ CommandLineDatabaseToolMain.java     # parses args, opens the connection, starts the REPL
├─ cli/
│  ├─ CommandLineProgram.java           # interactive loop, commands, confirmations
│  └─ SqlCompleter.java                 # JLine completer (tables/columns)
├─ code/
│  └─ Command.java                      # built‑in commands enum (HELP, EXIT, FILE, TOGGLE_AUTOCOMMIT)
├─ database/
│  ├─ DBConnectionManager.java          # loads JDBC drivers, creates connections
│  └─ QueryExecutor.java                # runs queries and .sql files, prints results
└─ util/
   ├─ CommonUtil.java                   # command‑line arg parsing (--key value)
   ├─ ConsoleUtil.java                  # password prompt (System.console fallback)
   └─ PrintUtil.java                    # usage/help and table rendering

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Troubleshooting

• "Unsupported driver" – Check the --driver flag. Must be postgres, mysql, oracle, or mssql.
• "Connection failed" – Verify host/port, database name, credentials, and whether the DB accepts TCP connections.
• SSL/Timezone parameters – Add them in your JDBC URL (e.g., ?sslmode=require for PostgreSQL).
• Oracle service name vs SID – Use the correct URL form for your environment.

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