sql-string-builder

This package provides utilities for building SQL query strings in a safe, composable, and parameterized manner. It is designed to prevent SQL injection vulnerabilities and enhance code readability when constructing complex queries.

Primary author: Alex Corrado

Installation

npm install sql-string-builder

Core Concepts

At the heart of this package are two main concepts:

1. QueryStringBuilder: A class that allows you to progressively build SQL queries by appending fragments and parameterized values.
2. sql tagged template literal: A function that simplifies the creation of QueryStringBuilder instances, enabling a more natural and readable way to write SQL queries within JavaScript/TypeScript code.

Additionally, the package offers UnsafeQueryLiteral for situations where direct string interpolation is necessary (with strong warnings) and helper functions for common SQL construction patterns.

sql Tagged Template Literal

import { sql } from "sql-string-builder";

The sql tagged template literal is the most convenient and recommended way to create QueryStringBuilder instances. It allows you to write SQL queries in a template literal syntax, embedding JavaScript/TypeScript expressions as parameterized values.

Usage:

const query = sql`SQL query text with ${parameter1} and ${parameter2}`;

• The template literal is tagged with sql.
• Placeholders ${expression} are used to embed JavaScript/TypeScript expressions. These expressions will be treated as parameterized values.
• The sql function returns a QueryStringBuilder instance.

Example:

import { sql } from "sql-string-builder";

const productName = "Awesome Gadget";
const price = 99.99;

const query = sql`
    SELECT *
    FROM products
    WHERE name = ${productName}
      AND price <= ${price}
`;

const [queryText, values] = query.build();
console.log(queryText); // Output: SELECT * FROM products WHERE name = $1 AND price <= $2
console.log(values); // Output: [ 'Awesome Gadget', 99.99 ]

UnsafeQueryLiteral

import { UnsafeQueryLiteral } from "sql-string-builder";

UnsafeQueryLiteral is a special type that wraps a string. When a QueryStringBuilder encounters an UnsafeQueryLiteral, it directly interpolates the string value into the SQL query without parameterization or escaping.

⚠️ WARNING: Use with Extreme Caution! ⚠️

UnsafeQueryLiteral should ONLY be used for parts of the SQL query that are absolutely guaranteed to be safe and not derived from user input or any untrusted source. Using UnsafeQueryLiteral with user-controlled strings creates a severe SQL injection vulnerability.

When to (Rarely) Use UnsafeQueryLiteral:

• For injecting static, hardcoded SQL keywords, identifiers (table names, column names), or functions that are known to be safe.
• In scenarios where parameterization is not possible for a specific part of the SQL syntax (e.g., table or column names in some database systems).

Example (Use with Caution - for illustration only):

import { sql, UnsafeQueryLiteral } from "sql-string-builder";

const tableName = new UnsafeQueryLiteral("users_table"); // Static, known table name
const columnName = new UnsafeQueryLiteral("username"); // Static, known column name

const query = sql`SELECT ${columnName} FROM ${tableName} WHERE id = ${123}`;

const [queryText, values] = query.build();
console.log(queryText); // Output: SELECT username FROM users_table WHERE id = $1
console.log(values); // Output: [ 123 ]

In most cases, you should avoid UnsafeQueryLiteral and rely on parameterized values and the QueryStringBuilder to construct your SQL queries safely.

QueryStringBuilder

import { QueryStringBuilder, sql } from "sql-string-builder";

QueryStringBuilder is the primary class in this package for constructing SQL queries. It provides a fluent interface for appending SQL fragments and parameterized values.

Constructor

constructor(
    tokenForIndex: (i: number) => string,
    queryTexts?: string[],
    values?: readonly any[]
)

While you can directly instantiate QueryStringBuilder, it is generally recommended to use the sql tagged template literal for easier creation.

Parameters (for direct instantiation - usually not needed):

• tokenForIndex: (i: number) => string: A function that, given an index i, returns the placeholder token for the i-th value. For PostgreSQL, this is typically (i) => "$" + (i + 1).
• queryTexts?: string[]: An array of string fragments that form the base SQL query.
• values?: readonly any[]: An optional array of values to be parameterized into the query.

append(part: QueryStringBuilder): QueryStringBuilder

Appends another QueryStringBuilder to the current builder. This is the core method for composing larger queries from smaller, reusable parts.

Parameters:

• part: QueryStringBuilder: The QueryStringBuilder to append.

Returns:

• QueryStringBuilder: Returns this (the current QueryStringBuilder) for method chaining.

Example:

import { sql } from "sql-string-builder";

const selectClause = sql`SELECT * FROM users`;
const whereClause = sql`WHERE age > ${18}`;

const query = selectClause.append(whereClause);

const [queryText, values] = query.build();
console.log(queryText); // Output: SELECT * FROM usersWHERE age > $1
console.log(values); // Output: [ 18 ]

appendRawString(part: string): QueryStringBuilder

Appends a raw string directly to the SQL query.

⚠️ WARNING: Use with Extreme Caution! ⚠️

Similar to UnsafeQueryLiteral, appendRawString bypasses parameterization and directly injects the provided string into the SQL query. This should only be used for safe, trusted, and non-user-controlled parts of the query.

Parameters:

• part: string: The raw string to append.

Returns:

• QueryStringBuilder: Returns this for method chaining.

Example (Use with Caution - for illustration only):

import { sql } from "sql-string-builder";

const orderByClause = sql`ORDER BY created_at`;
const direction = "DESC"; // Static, known direction

const query = orderByClause.appendRawString(` ${direction}`);

const [queryText, values] = query.build();
console.log(queryText); // Output: ORDER BY created_at DESC
console.log(values); // Output: []

clone(): QueryStringBuilder

Creates a new, mutable QueryStringBuilder that is a copy of the current builder. This is useful when you need to modify a query without affecting the original builder.

Returns:

• QueryStringBuilder: A new QueryStringBuilder instance with the same content as the original.

Example:

import { sql } from "sql-string-builder";

const baseQuery = sql`SELECT * FROM products`;
const query1 = baseQuery.clone().append(sql` WHERE price < ${100}`);
const query2 = baseQuery
    .clone()
    .append(sql` WHERE category = ${"Electronics"}`);

const [queryText1, values1] = query1.build();
console.log(queryText1); // Output: SELECT * FROM products WHERE price < $1
console.log(values1); // Output: [ 100 ]

const [queryText2, values2] = query2.build();
console.log(queryText2); // Output: SELECT * FROM products WHERE category = $1
console.log(values2); // Output: [ 'Electronics' ]

// baseQuery remains unchanged
const [baseQueryText, baseQueryValues] = baseQuery.build();
console.log(baseQueryText); // Output: SELECT * FROM products
console.log(baseQueryValues); // Output: []

build(): [queryText: string, values: any[] | undefined]

Finalizes the QueryStringBuilder and generates the SQL query string and an array of parameterized values. After calling build(), the QueryStringBuilder instance becomes frozen, and further modifications will result in errors.

Returns:

• [queryText: string, values: any[] | undefined]: An array containing two elements:
  • queryText: string: The complete SQL query string with parameter placeholders (e.g., $1, $2, etc.).
  • values: any[] | undefined: An array of values that correspond to the parameter placeholders in queryText. This array will be undefined if there are no parameterized values.

Example:

import { sql } from "sql-string-builder";

const name = "John Doe";
const age = 30;

const query = sql`INSERT INTO users (name, age) VALUES (${name}, ${age})`;
const [queryText, values] = query.build();

console.log(queryText); // Output: INSERT INTO users (name, age) VALUES ($1, $2)
console.log(values); // Output: [ 'John Doe', 30 ]

// You can now execute the queryText and values with your database client.

approximateLength(): number

Returns an approximate length of the SQL query string being built. This can be useful for performance optimizations or logging purposes.

Returns:

• number: An approximate length of the SQL query string.

Example:

import { sql } from "sql-string-builder";

const longQuery = sql``;
for (let i = 0; i < 100; i++) {
    longQuery.append(sql`SELECT * FROM table${i}; `);
}

console.log(longQuery.approximateLength()); // Output: A number representing the approximate length

Helper Functions

The sql-string-builder package provides several helper functions to simplify common SQL construction tasks.

joinSQL(items: readonly QueryStringBuilder[], separator: string): QueryStringBuilder

Joins an array of QueryStringBuilder instances into a single QueryStringBuilder, using the specified separator string between each item.

Parameters:

• items: readonly QueryStringBuilder[]: An array of QueryStringBuilder instances to join.
• separator: string: The string to use as a separator between the joined items.

Returns:

• QueryStringBuilder: A new QueryStringBuilder representing the joined SQL fragments.

Example:

import { sql, joinSQL } from "sql-string-builder";

const conditions = [
    sql`age > ${18}`,
    sql`city = ${"New York"}`,
    sql`is_active = ${true}`,
];

const whereClause = sql`WHERE `.append(joinSQL(conditions, " AND "));

const query = sql`SELECT * FROM users `.append(whereClause);

const [queryText, values] = query.build();
console.log(queryText); // Output: SELECT * FROM users WHERE age > $1 AND city = $2 AND is_active = $3
console.log(values); // Output: [ 18, 'New York', true ]

commaJoinSQL(items: readonly QueryStringBuilder[]): QueryStringBuilder

A convenience function that joins an array of QueryStringBuilder instances using a comma and a space (, ) as the separator. This is commonly used for constructing comma-separated lists in SQL (e.g., in SELECT or INSERT statements).

Parameters:

• items: readonly QueryStringBuilder[]: An array of QueryStringBuilder instances to join.

Returns:

• QueryStringBuilder: A new QueryStringBuilder representing the comma-separated SQL fragments.

Example:

import { sql, commaJoinSQL } from "sql-string-builder";

const columns = [sql`name`, sql`email`, sql`created_at`];

const selectClause = sql`SELECT `
    .append(commaJoinSQL(columns))
    .append(sql` FROM users`);

const [queryText, values] = selectClause.build();
console.log(queryText); // Output: SELECT name, email, created_at FROM users
console.log(values); // Output: []

commaJoinStringsToSQL(strings: readonly string[]): QueryStringBuilder

A helper function that takes an array of strings and converts them into a comma-separated list of parameterized values within a QueryStringBuilder.

Parameters:

• strings: readonly string[]: An array of strings to be joined and parameterized.

Returns:

• QueryStringBuilder: A new QueryStringBuilder representing the comma-separated parameterized string values.

Example:

import { sql, commaJoinStringsToSQL } from "sql-string-builder";

const userEmails = [
    "user1@example.com",
    "user2@example.com",
    "user3@example.com",
];

const whereClause = sql`WHERE email IN (`
    .append(commaJoinStringsToSQL(userEmails))
    .append(sql`)`);

const query = sql`SELECT * FROM users `.append(whereClause);

const [queryText, values] = query.build();
console.log(queryText); // Output: SELECT * FROM users WHERE email IN ($1, $2, $3)
console.log(values); // Output: [ 'user1@example.com', 'user2@example.com', 'user3@example.com' ]

Security Considerations

• SQL Injection Prevention: This package is designed to help prevent SQL injection vulnerabilities by promoting the use of parameterized queries. Always use parameterized values (using ${expression} within the sql template literal) for any data that originates from user input or untrusted sources.
• UnsafeQueryLiteral and appendRawString: These features should be used with extreme caution and only when absolutely necessary for static, trusted parts of the SQL query. Improper use can reintroduce SQL injection risks. Thoroughly review and understand the security implications before using them.

By using the sql-string-builder package correctly, you can build robust, readable, and secure SQL queries in your applications.

License

MIT