Production Relational SchemaIntermediate → Advanced

Banking

Customers, accounts, transactions, branches and loans.

6 Tables50K+ RecordsTransactionsCTEWindow Functions

Interactive SQL Playground & Query Runner

In-Browser Sandbox

Run realistic queries against the Banking database. Write custom SQL or solve high-yield interview problems.

Interview Challenge:

easy

High-Balance Customer Accounts with Branch Details

List all accounts with a balance greater than ₹30,000, along with customer name and city.

INNER JOINFiltering

query.sql

Press Ctrl + Enter to execute

Entity Relationship (ER) & Foreign Key Architecture

Referential integrity mappings and table cardinalities

5 Key Relations

1:NOwns Accounts

customers

client_id

accounts

client_id

1:NMapped To

accounts

account_id

account_branch

account_id

1:NServices Account

branches

branch_id

account_branch

branch_id

1:NRecords Transactions

accounts

account_id

transactions

account_id

1:NBorrower Of

customers

client_id

loans

client_id

Relational Tables & Column Data Types

Field definitions, types, and primary keys for query construction

6 tables total

customers

3 cols

PKclient_id

INT

client_name

VARCHAR(90)

city

VARCHAR(60)

accounts

5 cols

PKaccount_id

INT

PKclient_id

INT

account_type

VARCHAR(30)

opened_on

DATE

balance

DECIMAL(12,2)

branches

3 cols

PKbranch_id

INT

branch_name

VARCHAR(80)

city

VARCHAR(60)

account_branch

2 cols

PKaccount_id

INT

PKbranch_id

INT

transactions

5 cols

PKentry_id

INT

PKaccount_id

INT

entry_date

DATE

entry_type

VARCHAR(20)

amount

DECIMAL(12,2)

loans

4 cols

PKloan_id

INT

PKclient_id

INT

principal

DECIMAL(12,2)

status

VARCHAR(20)

Runnable DDL Setup & Seed Script

Run directly in MySQL Workbench, pgAdmin, DBeaver, or terminal

CREATE DATABASE IF NOT EXISTS studyflow_banking;
USE studyflow_banking;

CREATE TABLE customers (
  client_id INT PRIMARY KEY,
  client_name VARCHAR(90) NOT NULL,
  city VARCHAR(60)
);

CREATE TABLE accounts (
  account_id INT PRIMARY KEY,
  client_id INT,
  account_type VARCHAR(30),
  opened_on DATE,
  balance DECIMAL(12,2),
  FOREIGN KEY (client_id) REFERENCES customers(client_id)
);

CREATE TABLE branches (
  branch_id INT PRIMARY KEY,
  branch_name VARCHAR(80),
  city VARCHAR(60)
);

CREATE TABLE account_branch (
  account_id INT,
  branch_id INT,
  PRIMARY KEY (account_id, branch_id),
  FOREIGN KEY (account_id) REFERENCES accounts(account_id),
  FOREIGN KEY (branch_id) REFERENCES branches(branch_id)
);

CREATE TABLE transactions (
  entry_id INT PRIMARY KEY,
  account_id INT,
  entry_date DATE,
  entry_type VARCHAR(20),
  amount DECIMAL(12,2),
  FOREIGN KEY (account_id) REFERENCES accounts(account_id)
);

CREATE TABLE loans (
  loan_id INT PRIMARY KEY,
  client_id INT,
  principal DECIMAL(12,2),
  status VARCHAR(20),
  FOREIGN KEY (client_id) REFERENCES customers(client_id)
);

INSERT INTO customers VALUES
(1,'Ira Mehta','Jaipur'),(2,'Dev Nair','Kochi'),(3,'Mira Shah','Surat'),(4,'Kabir Singh','Pune');

INSERT INTO accounts VALUES
(101,1,'Savings','2022-01-10',42000),(102,1,'Current','2023-06-18',85000),
(103,2,'Savings','2024-02-11',27000),(104,3,'Savings','2021-09-04',64000),(105,4,'Savings','2025-01-21',19000);

INSERT INTO branches VALUES
(1,'Central Jaipur','Jaipur'),(2,'Harbor Kochi','Kochi'),(3,'Market Pune','Pune');

INSERT INTO account_branch VALUES
(101,1),(102,1),(103,2),(104,1),(105,3);

INSERT INTO transactions VALUES
(1,101,'2026-01-03','credit',5000),(2,101,'2026-01-08','debit',1200),
(3,101,'2026-02-01','credit',3000),(4,102,'2026-02-05','debit',10000),
(5,103,'2026-02-11','credit',4500),(6,104,'2026-03-02','debit',2500),
(7,104,'2026-03-08','credit',8000),(8,105,'2026-03-12','debit',900);

INSERT INTO loans VALUES
(201,1,120000,'active'),(202,2,75000,'closed'),(203,4,90000,'active');