sql-flex-query

A lightweight, dialect-aware SQL query builder that enhances base query templates with dynamic WHERE, HAVING, ORDER BY, pagination, and more. Also provides helpers for building INSERT, UPDATE, and DELETE queries with dialect-specific placeholders.

Write once, run on any SQL database — PostgreSQL, MySQL, SQLite, SQL Server, Oracle, CockroachDB, Snowflake. Need another database? Extend BaseDialect to add custom dialect support (see below).

Supported Databases

Database
PostgreSQL
MySQL
SQLite
SQL Server
Oracle
CockroachDB
Snowflake

Why sql-flex-query?

The Problem

Different SQL databases use different placeholder styles, identifier quoting, and pagination syntax:

Database	Placeholders	Identifier Quoting	Pagination
PostgreSQL	`$1, $2`	`"double quotes"`	`LIMIT/OFFSET`
MySQL	`?`	`backticks`	`LIMIT/OFFSET`
SQLite	`?`	`"double quotes"`	`LIMIT/OFFSET`
SQL Server	`@p1, @p2`	`[brackets]`	`OFFSET/FETCH`
Oracle	`:1, :2`	`"double quotes"`	`OFFSET/FETCH`
CockroachDB	`$1, $2`	`"double quotes"`	`LIMIT/OFFSET`
Snowflake	`?`	`"double quotes"`	`LIMIT/OFFSET`

Maintaining separate queries for each dialect is error-prone and hard to maintain.

The Solution

sql-flex-query lets you write one query that automatically adapts to any supported dialect. It handles:

✅ Placeholder conversion ($1 → ? → @p1)
✅ Identifier quoting ("col" → `col` → [col])
✅ Pagination syntax (LIMIT/OFFSET vs OFFSET/FETCH)
✅ TypeScript type safety
✅ Dynamic WHERE, ORDER BY, text search (OR conditions)
✅ GROUP BY and HAVING support
✅ Column mapping for clean code

Quick Comparison

Feature	sql-flex-query	Knex.js	Raw SQL	ORM (Prisma/TypeORM)
Multi-dialect	✅ Automatic	✅ Yes	❌ Manual	✅ Limited
Use existing SQL	✅ Yes	❌ No	✅ Yes	❌ No
TypeScript support	✅ Full	⚠️ Partial	❌ None	✅ Full
Learning curve	🟢 Low	🟡 Medium	🟢 Low	🔴 High
Migrations	❌ No	✅ Yes	❌ No	✅ Yes
Size	~15KB	~100KB	0KB	~200KB+
Flexibility	🟢 High	🟡 Medium	🟢 High	🔴 Low

Choose sql-flex-query if: You need multi-dialect support, want to use your existing SQL, value TypeScript types, and don't need built-in migrations.

Installation

npm install sql-flex-query

Quick Start

1. Simple Query with Filters

const { buildQueries } = require("sql-flex-query");

const BASE = `
  SELECT /*SELECT_COLUMNS*/
  FROM users u
  /*WHERE_CLAUSE*/
  /*ORDER_BY*/
  /*LIMIT_CLAUSE*/
`;

const result = buildQueries(
  BASE,
  [
    { key: "status", operation: "EQ", value: "ACTIVE" },
    { key: "age", operation: "GTE", value: 18 },
  ],
  [],
  [{ key: "createdAt", direction: "DESC" }],
  1,  // page
  10, // page size
  { createdAt: "u.created_at" }, // columnMapper (optional)
  ["id", "name", "email", "createdAt"], // selectColumns (optional)
  "postgres" // dialect (optional, defaults to postgres)
);

console.log(result.searchQuery);
// SELECT u.id AS "id", u.name AS "name", u.email AS "email", u.created_at AS "createdAt"
// FROM users u
// WHERE "status" = $1 AND "age" >= $2
// ORDER BY u.created_at DESC
// LIMIT 10 OFFSET 0

console.log(result.params);
// ['ACTIVE', 18]

That's it! The same code works for MySQL, SQLite, SQL Server, Oracle, CockroachDB, and Snowflake—just change the dialect parameter.

Basic Examples

1. Simple SELECT with WHERE and Pagination

const { buildQueries } = require("sql-flex-query");

const BASE = `
  SELECT /*SELECT_COLUMNS*/
  FROM users u
  /*WHERE_CLAUSE*/
  /*ORDER_BY*/
  /*LIMIT_CLAUSE*/
`;

const result = buildQueries(
  BASE,
  [
    { key: "status", operation: "EQ", value: "ACTIVE" },
    { key: "age", operation: "GTE", value: 18 },
  ],
  [],
  [{ key: "createdAt", direction: "DESC" }],
  1,
  10,
  { createdAt: "u.created_at" },
  ["id", "name", "email", "createdAt"],
);
// searchQuery: SELECT u.id AS "id", ... WHERE "status" = $1 AND u.created_at >= $2 ORDER BY ... LIMIT 10 OFFSET 0
// params: ['ACTIVE', 18]

2. BETWEEN — Range Filtering

Use BETWEEN to filter a column within a half-open range ([min, max)). Pass a two-element array as the value.

const result = buildQueries({
  baseQueryTemplate: `
    SELECT /*SELECT_COLUMNS*/
    FROM orders o
    /*WHERE_CLAUSE*/
    /*ORDER_BY*/
    /*LIMIT_CLAUSE*/
  `,
  whereParams: [
    // Matches: o.total >= 100 AND o.total < 500
    { key: "total", operation: "BETWEEN", value: [100, 500] },
    // Matches: o.created_at >= '2024-01-01' AND o.created_at < '2025-01-01'
    { key: "createdAt", operation: "BETWEEN", value: ["2024-01-01", "2025-01-01"] },
  ],
  columnMapper: { total: "o.total", createdAt: "o.created_at" },
  dialect: "postgres",
});
// WHERE (o.total >= $1 AND o.total < $2) AND (o.created_at >= $3 AND o.created_at < $4)
// params: [100, 500, '2024-01-01', '2025-01-01']

Note: BETWEEN generates (col >= min AND col < max) — inclusive lower bound, exclusive upper bound. The value must be an array of exactly two elements.

3. Text Search (OR) + Filters (AND)

const result = buildQueries({
  baseQueryTemplate: `
    SELECT /*SELECT_COLUMNS*/
    FROM products p
    /*WHERE_CLAUSE*/
    /*ORDER_BY*/
    /*LIMIT_CLAUSE*/
  `,
  textSearchParams: [
    { key: "name", operation: "LIKE", value: "%laptop%", ignoreCase: true },
    {
      key: "description",
      operation: "LIKE",
      value: "%laptop%",
      ignoreCase: true,
    },
  ],
  whereParams: [
    { key: "status", operation: "EQ", value: "PUBLISHED" },
    { key: "price", operation: "LTE", value: 2000 },
    { key: "deleted_at", operation: "NULL" },
  ],
  sortBy: [{ key: "price", direction: "ASC" }],
  page: 1,
  size: 20,
  dialect: "postgres",
});
// WHERE (LOWER("name") LIKE $1 OR LOWER("description") LIKE $2)
//   AND "status" = $3 AND "price" <= $4 AND "deleted_at" IS NULL
// params: ['%laptop%', '%laptop%', 'PUBLISHED', 2000]

Complex Examples

4. Multi-table JOIN with Column Mapping

const { buildQueries } = require("sql-flex-query");

const BASE = `
  SELECT /*SELECT_COLUMNS*/
  FROM orders o
  JOIN customers c ON c.id = o.customer_id
  JOIN order_items oi ON oi.order_id = o.id
  JOIN products p ON p.id = oi.product_id
  /*WHERE_CLAUSE*/
  /*ORDER_BY*/
  /*LIMIT_CLAUSE*/
`;

const columnMapper = {
  orderId: "o.id",
  orderDate: "o.created_at",
  orderStatus: "o.status",
  customerName: "c.name",
  customerEmail: "c.email",
  productName: "p.name",
  quantity: "oi.quantity",
  unitPrice: "oi.unit_price",
};

const result = buildQueries({
  baseQueryTemplate: BASE,
  columnMapper,
  selectColumns: [
    "orderId",
    "orderDate",
    "orderStatus",
    "customerName",
    "customerEmail",
    "productName",
    "quantity",
    "unitPrice",
  ],
  whereParams: [
    { key: "orderStatus", operation: "IN", value: ["SHIPPED", "DELIVERED"] },
    { key: "orderDate", operation: "GTE", value: "2024-01-01" },
    { key: "orderDate", operation: "LTE", value: "2024-12-31" },
    { key: "unitPrice", operation: "GT", value: 0 },
  ],
  textSearchParams: [
    {
      key: "customerName",
      operation: "LIKE",
      value: "%john%",
      ignoreCase: true,
    },
    {
      key: "customerEmail",
      operation: "LIKE",
      value: "%john%",
      ignoreCase: true,
    },
    {
      key: "productName",
      operation: "LIKE",
      value: "%john%",
      ignoreCase: true,
    },
  ],
  sortBy: [
    { key: "orderDate", direction: "DESC" },
    { key: "customerName", direction: "ASC" },
  ],
  page: 1,
  size: 25,
  dialect: "postgres",
});

// searchQuery:
// SELECT o.id AS "orderId", o.created_at AS "orderDate", o.status AS "orderStatus",
//        c.name AS "customerName", c.email AS "customerEmail",
//        p.name AS "productName", oi.quantity AS "quantity", oi.unit_price AS "unitPrice"
// FROM orders o
// JOIN customers c ON c.id = o.customer_id
// JOIN order_items oi ON oi.order_id = o.id
// JOIN products p ON p.id = oi.product_id
// WHERE (LOWER(c.name) LIKE $1 OR LOWER(c.email) LIKE $2 OR LOWER(p.name) LIKE $3)
//   AND o.status IN ($4, $5)
//   AND o.created_at >= $6 AND o.created_at <= $7
//   AND oi.unit_price > $8
// ORDER BY o.created_at DESC, c.name ASC
// LIMIT 25 OFFSET 0
//
// params: ['%john%', '%john%', '%john%', 'SHIPPED', 'DELIVERED', '2024-01-01', '2024-12-31', 0]

5. GROUP BY + HAVING (Aggregation Reports)

const { buildQueries } = require("sql-flex-query");

// GROUP BY is part of the template.
// The builder handles WHERE (before GROUP BY) and HAVING (after GROUP BY) automatically.
const BASE = `
  SELECT /*SELECT_COLUMNS*/
  FROM orders o
  JOIN customers c ON c.id = o.customer_id
  JOIN order_items oi ON oi.order_id = o.id
  /*WHERE_CLAUSE*/
  GROUP BY c.id, c.name, c.email
  /*HAVING_CLAUSE*/
  /*ORDER_BY*/
  /*LIMIT_CLAUSE*/
`;

const columnMapper = {
  customerName: "c.name",
  customerEmail: "c.email",
  orderCount: "COUNT(DISTINCT o.id)",
  totalSpent: "SUM(oi.quantity * oi.unit_price)",
  avgOrderValue: "AVG(oi.quantity * oi.unit_price)",
  orderDate: "o.created_at",
  orderStatus: "o.status",
};

const result = buildQueries({
  baseQueryTemplate: BASE,
  columnMapper,
  selectColumns: [
    "customerName",
    "customerEmail",
    "orderCount",
    "totalSpent",
    "avgOrderValue",
  ],
  whereParams: [
    // WHERE filters — applied BEFORE GROUP BY
    { key: "orderStatus", operation: "IN", value: ["COMPLETED", "DELIVERED"] },
    { key: "orderDate", operation: "GTE", value: "2024-01-01" },
    { key: "orderDate", operation: "LTE", value: "2024-12-31" },

    // HAVING filters — set having: true — applied AFTER GROUP BY
    { key: "orderCount", operation: "GTE", value: 5, having: true },
    { key: "totalSpent", operation: "GTE", value: 1000, having: true },
  ],
  sortBy: [{ key: "totalSpent", direction: "DESC" }],
  page: 1,
  size: 10,
  dialect: "postgres",
});

// searchQuery:
// SELECT c.name AS "customerName", c.email AS "customerEmail",
//        COUNT(DISTINCT o.id) AS "orderCount",
//        SUM(oi.quantity * oi.unit_price) AS "totalSpent",
//        AVG(oi.quantity * oi.unit_price) AS "avgOrderValue"
// FROM orders o
// JOIN customers c ON c.id = o.customer_id
// JOIN order_items oi ON oi.order_id = o.id
// WHERE o.status IN ($1, $2) AND o.created_at >= $3 AND o.created_at <= $4
// GROUP BY c.id, c.name, c.email
// HAVING COUNT(DISTINCT o.id) >= $5 AND SUM(oi.quantity * oi.unit_price) >= $6
// ORDER BY SUM(oi.quantity * oi.unit_price) DESC
// LIMIT 10 OFFSET 0
//
// params: ['COMPLETED', 'DELIVERED', '2024-01-01', '2024-12-31', 5, 1000]

6. GROUP BY with modifyCountQuery

When using GROUP BY, the default COUNT gives wrong results. Use modifyCountQuery to wrap the count:

const BASE_WITH_GROUP = `
  SELECT /*SELECT_COLUMNS*/
  FROM app_messages msg
  LEFT JOIN app_locations loc ON msg.location_id = loc.id
  JOIN app_tasks task ON task.id = msg.task_id
  JOIN app_task_case_link tcl ON tcl.task_id = task.id
  JOIN (
    SELECT DISTINCT task_id, case_ref, org_code
    FROM app_case_snapshot WHERE is_current = true
  ) cs ON cs.task_id = tcl.task_id AND cs.case_ref = tcl.case_ref
  /*WHERE_CLAUSE*/
  GROUP BY DATE(task.created_at), cs.org_code, msg.is_structured
  /*HAVING_CLAUSE*/
  /*ORDER_BY*/ /*LIMIT_CLAUSE*/
`;

const columnMapper = {
  createdDate: "DATE(task.created_at)",
  organizationCode: "cs.org_code",
  structured: "msg.is_structured",
  messageCount: "COUNT(msg.id)",
  locationName: "loc.display_name",
  state: "msg.state",
};

const result = buildQueries({
  baseQueryTemplate: BASE_WITH_GROUP,
  columnMapper,
  selectColumns: [
    "createdDate",
    "organizationCode",
    "structured",
    "messageCount",
  ],
  whereParams: [
    { key: "state", operation: "EQ", value: "PROCESSED" },
    { key: "locationName", operation: "NOT_NULL" },
    { key: "messageCount", operation: "GT", value: 10, having: true },
  ],
  sortBy: [
    { key: "createdDate", direction: "DESC" },
    { key: "messageCount", direction: "DESC" },
  ],
  page: 1,
  size: 20,
  dialect: "postgres",
  // Wrap count query to count groups, not rows within groups
  modifyCountQuery: (query) =>
    `SELECT COUNT(*) AS count FROM (${query}) AS grouped_count`,
});

// countQuery:
// SELECT COUNT(*) AS count FROM (
//   SELECT 1 FROM app_messages msg
//   LEFT JOIN app_locations loc ON msg.location_id = loc.id
//   JOIN app_tasks task ON task.id = msg.task_id
//   JOIN app_task_case_link tcl ON tcl.task_id = task.id
//   JOIN (
//     SELECT DISTINCT task_id, case_ref, org_code
//     FROM app_case_snapshot WHERE is_current = true
//   ) cs ON cs.task_id = tcl.task_id AND cs.case_ref = tcl.case_ref
//   WHERE msg.state = $1 AND loc.display_name IS NOT NULL
//   GROUP BY DATE(task.created_at), cs.org_code, msg.is_structured
//   HAVING COUNT(msg.id) > $2
// ) AS grouped_count

7. LEFT JOIN + DISTINCT (Fluent API)

const { QueryBuilder } = require("sql-flex-query");

const BASE = `
  SELECT /*SELECT_COLUMNS*/
  FROM employees e
  LEFT JOIN departments d ON d.id = e.department_id
  LEFT JOIN employee_skills es ON es.employee_id = e.id
  LEFT JOIN skills s ON s.id = es.skill_id
  /*WHERE_CLAUSE*/
  /*ORDER_BY*/
  /*LIMIT_CLAUSE*/
`;

const result = new QueryBuilder("postgres")
  .baseQuery(BASE)
  .columnMapper({
    employeeId: "e.id",
    employeeName: "e.name",
    employeeEmail: "e.email",
    departmentName: "d.name",
    hireDate: "e.hire_date",
    salary: "e.salary",
    skillName: "s.name",
  })
  .select(["employeeId", "employeeName", "employeeEmail", "departmentName"])
  .distinct()
  .where([
    {
      key: "departmentName",
      operation: "IN",
      value: ["Engineering", "Product", "Design"],
    },
    { key: "hireDate", operation: "GTE", value: "2023-01-01" },
    { key: "salary", operation: "GTE", value: 50000 },
    { key: "salary", operation: "LTE", value: 150000 },
  ])
  .textSearch([
    {
      key: "employeeName",
      operation: "LIKE",
      value: "%sarah%",
      ignoreCase: true,
    },
    {
      key: "employeeEmail",
      operation: "LIKE",
      value: "%sarah%",
      ignoreCase: true,
    },
    { key: "skillName", operation: "LIKE", value: "%sarah%", ignoreCase: true },
  ])
  .orderBy([
    { key: "departmentName", direction: "ASC" },
    { key: "employeeName", direction: "ASC" },
  ])
  .paginate(2, 15)
  .build();

// searchQuery:
// SELECT DISTINCT e.id AS "employeeId", e.name AS "employeeName",
//        e.email AS "employeeEmail", d.name AS "departmentName"
// FROM employees e
// LEFT JOIN departments d ON d.id = e.department_id
// LEFT JOIN employee_skills es ON es.employee_id = e.id
// LEFT JOIN skills s ON s.id = es.skill_id
// WHERE (LOWER(e.name) LIKE $1 OR LOWER(e.email) LIKE $2 OR LOWER(s.name) LIKE $3)
//   AND d.name IN ($4, $5, $6)
//   AND e.hire_date >= $7 AND e.salary >= $8 AND e.salary <= $9
// ORDER BY d.name ASC, e.name ASC
// LIMIT 15 OFFSET 15
//
// params: ['%sarah%', '%sarah%', '%sarah%', 'Engineering', 'Product', 'Design',
//          '2023-01-01', 50000, 150000]

8. Sales Dashboard (Fluent API + GROUP BY + HAVING + MSSQL)

const { QueryBuilder } = require("sql-flex-query");

const BASE = `
  SELECT /*SELECT_COLUMNS*/
  FROM sales s
  JOIN sales_reps sr ON sr.id = s.rep_id
  JOIN regions r ON r.id = sr.region_id
  JOIN products p ON p.id = s.product_id
  JOIN product_categories pc ON pc.id = p.category_id
  /*WHERE_CLAUSE*/
  GROUP BY r.name, sr.name, pc.name, YEAR(s.sale_date), MONTH(s.sale_date)
  /*HAVING_CLAUSE*/
  /*ORDER_BY*/ /*LIMIT_CLAUSE*/
`;

const result = new QueryBuilder("mssql")
  .baseQuery(BASE)
  .columnMapper({
    regionName: "r.name",
    repName: "sr.name",
    categoryName: "pc.name",
    saleYear: "YEAR(s.sale_date)",
    saleMonth: "MONTH(s.sale_date)",
    totalRevenue: "SUM(s.amount)",
    totalUnits: "SUM(s.quantity)",
    dealCount: "COUNT(s.id)",
    avgDealSize: "AVG(s.amount)",
    saleDate: "s.sale_date",
    saleStatus: "s.status",
  })
  .select([
    "regionName",
    "repName",
    "categoryName",
    "saleYear",
    "saleMonth",
    "totalRevenue",
    "totalUnits",
    "dealCount",
    "avgDealSize",
  ])
  .where([
    { key: "saleDate", operation: "GTE", value: "2024-01-01" },
    { key: "saleDate", operation: "LTE", value: "2024-12-31" },
    { key: "saleStatus", operation: "EQ", value: "CLOSED_WON" },
    {
      key: "regionName",
      operation: "IN",
      value: ["North America", "Europe", "APAC"],
    },
  ])
  .having([
    { key: "totalRevenue", operation: "GTE", value: 50000 },
    { key: "dealCount", operation: "GTE", value: 3 },
  ])
  .orderBy([
    { key: "totalRevenue", direction: "DESC" },
    { key: "regionName", direction: "ASC" },
  ])
  .paginate(1, 20)
  .modifyCountQuery((query) => `SELECT COUNT(*) AS count FROM (${query}) AS t`)
  .build();

// searchQuery (SQL Server):
// SELECT r.name AS [regionName], sr.name AS [repName], pc.name AS [categoryName],
//        YEAR(s.sale_date) AS [saleYear], MONTH(s.sale_date) AS [saleMonth],
//        SUM(s.amount) AS [totalRevenue], SUM(s.quantity) AS [totalUnits],
//        COUNT(s.id) AS [dealCount], AVG(s.amount) AS [avgDealSize]
// FROM sales s
// JOIN sales_reps sr ON sr.id = s.rep_id
// JOIN regions r ON r.id = sr.region_id
// JOIN products p ON p.id = s.product_id
// JOIN product_categories pc ON pc.id = p.category_id
// WHERE s.sale_date >= @p1 AND s.sale_date <= @p2
//   AND s.status = @p3 AND r.name IN (@p4, @p5, @p6)
// GROUP BY r.name, sr.name, pc.name, YEAR(s.sale_date), MONTH(s.sale_date)
// HAVING SUM(s.amount) >= @p7 AND COUNT(s.id) >= @p8
// ORDER BY SUM(s.amount) DESC, r.name ASC OFFSET 0 ROWS FETCH NEXT 20 ROWS ONLY
//
// params: ['2024-01-01', '2024-12-31', 'CLOSED_WON',
//          'North America', 'Europe', 'APAC', 50000, 3]

9. Subquery JOIN with MySQL (Fluent API)

const { QueryBuilder } = require("sql-flex-query");

const BASE = `
  SELECT /*SELECT_COLUMNS*/
  FROM users u
  JOIN (
    SELECT user_id,
           COUNT(*) as login_count,
           MAX(login_at) as last_login
    FROM login_history
    WHERE login_at >= '2024-01-01'
    GROUP BY user_id
  ) lh ON lh.user_id = u.id
  LEFT JOIN user_subscriptions us ON us.user_id = u.id AND us.is_active = true
  LEFT JOIN plans p ON p.id = us.plan_id
  /*WHERE_CLAUSE*/
  /*ORDER_BY*/
  /*LIMIT_CLAUSE*/
`;

const result = new QueryBuilder("mysql")
  .baseQuery(BASE)
  .columnMapper({
    userId: "u.id",
    userName: "u.name",
    userEmail: "u.email",
    loginCount: "lh.login_count",
    lastLogin: "lh.last_login",
    planName: "p.name",
    userStatus: "u.status",
    userRole: "u.role",
  })
  .select([
    "userId",
    "userName",
    "userEmail",
    "loginCount",
    "lastLogin",
    "planName",
  ])
  .where([
    { key: "userStatus", operation: "EQ", value: "ACTIVE" },
    { key: "loginCount", operation: "GTE", value: 10 },
    {
      key: "userRole",
      operation: "IN",
      value: ["ADMIN", "PREMIUM", "ENTERPRISE"],
    },
    { key: "planName", operation: "NOT_NULL" },
  ])
  .textSearch([
    {
      key: "userName",
      operation: "LIKE",
      value: "%search_term%",
      ignoreCase: true,
    },
    {
      key: "userEmail",
      operation: "LIKE",
      value: "%search_term%",
      ignoreCase: true,
    },
  ])
  .orderBy([
    { key: "loginCount", direction: "DESC" },
    { key: "lastLogin", direction: "DESC" },
  ])
  .paginate(1, 50)
  .build();

// searchQuery (MySQL):
// SELECT u.id AS \`userId\`, u.name AS \`userName\`, u.email AS \`userEmail\`,
//        lh.login_count AS \`loginCount\`, lh.last_login AS \`lastLogin\`,
//        p.name AS \`planName\`
// FROM users u
// JOIN (...) lh ON lh.user_id = u.id
// LEFT JOIN user_subscriptions us ON us.user_id = u.id AND us.is_active = true
// LEFT JOIN plans p ON p.id = us.plan_id
// WHERE (\`userName\` LIKE ? OR \`userEmail\` LIKE ?)
//   AND u.status = ? AND lh.login_count >= ?
//   AND u.role IN (?, ?, ?) AND p.name IS NOT NULL
// ORDER BY lh.login_count DESC, lh.last_login DESC
// LIMIT 50 OFFSET 0
//
// params: ['%search_term%', '%search_term%', 'ACTIVE', 10, 'ADMIN', 'PREMIUM', 'ENTERPRISE']

Dialect Helpers for INSERT / UPDATE / DELETE

The dialectHelpers() factory provides dialect-aware utilities for building INSERT, UPDATE, DELETE, and custom queries — without prescribing a specific pattern. You get the building blocks; you compose the final SQL.

10. INSERT Query (Postgres)

const { dialectHelpers } = require("sql-flex-query");

const h = dialectHelpers("postgres");
const columnMapper = { name: "u.name", email: "u.email", role: "u.role" };

const data = { name: "John Doe", email: "john@example.com", role: "ADMIN" };
const { columns, placeholders, params } = h.buildInsertValues(
  data,
  columnMapper,
);

const query = `INSERT INTO users (${columns.join(", ")}) VALUES (${placeholders.join(", ")}) RETURNING *`;
// query:  INSERT INTO users (u.name, u.email, u.role) VALUES ($1, $2, $3) RETURNING *
// params: ['John Doe', 'john@example.com', 'ADMIN']

Same query with MySQL:

const h = dialectHelpers("mysql");
const { columns, placeholders, params } = h.buildInsertValues(
  data,
  columnMapper,
);

const query = `INSERT INTO users (${columns.join(", ")}) VALUES (${placeholders.join(", ")})`;
// query:  INSERT INTO users (u.name, u.email, u.role) VALUES (?, ?, ?)
// params: ['John Doe', 'john@example.com', 'ADMIN']

11. UPDATE Query with WHERE (Postgres & MSSQL)

Use buildWhereClause with existingParams — the same API you use for SELECT WHERE clauses. When you pass the SET params array, placeholder numbering continues automatically.

const { dialectHelpers } = require("sql-flex-query");

const h = dialectHelpers("postgres");
const columnMapper = { name: "u.name", email: "u.email", id: "u.id" };

// 1. Build SET clause
const data = { name: "Jane Doe", email: "jane@example.com" };
const { setClause, params } = h.buildSetClause(data, columnMapper);
// setClause: 'u.name = $1, u.email = $2'
// params:    ['Jane Doe', 'jane@example.com']

// 2. Build WHERE — pass `params` so placeholders continue from $3
const { clause } = h.buildWhereClause(
  [{ key: "id", operation: "EQ", value: 42 }],
  [],
  columnMapper,
  params, // ← same params array
);

const query = `UPDATE users SET ${setClause}${clause} RETURNING *`;
// query:  UPDATE users SET u.name = $1, u.email = $2 WHERE u.id = $3 RETURNING *
// params: ['Jane Doe', 'jane@example.com', 42]

Same query with MSSQL:

const h = dialectHelpers("mssql");
const { setClause, params } = h.buildSetClause(data, columnMapper);

const { clause } = h.buildWhereClause(
  [{ key: "id", operation: "EQ", value: 42 }],
  [],
  columnMapper,
  params,
);

const query = `UPDATE users SET ${setClause}${clause}`;
// query:  UPDATE users SET u.name = @p1, u.email = @p2 WHERE u.id = @p3
// params: ['Jane Doe', 'jane@example.com', 42]

UPDATE with complex WHERE (multiple criteria, IN, etc.):

const h = dialectHelpers("postgres");
const columnMapper = {
  status: "u.status",
  role: "u.role",
  lastLogin: "u.last_login",
};

const { setClause, params } = h.buildSetClause(
  { status: "INACTIVE" },
  columnMapper,
);

// Same buildWhereClause you'd use for SELECT — just pass params to continue numbering
const { clause } = h.buildWhereClause(
  [
    { key: "role", operation: "IN", value: ["GUEST", "TRIAL"] },
    { key: "lastLogin", operation: "LTE", value: "2023-01-01" },
  ],
  [],
  columnMapper,
  params,
);

const query = `UPDATE users SET ${setClause}${clause}`;
// query:  UPDATE users SET u.status = $1 WHERE u.role IN ($2, $3) AND u.last_login <= $4
// params: ['INACTIVE', 'GUEST', 'TRIAL', '2023-01-01']

12. DELETE Query with WHERE (Postgres)

const { dialectHelpers } = require("sql-flex-query");

const h = dialectHelpers("postgres");
const columnMapper = {
  id: "u.id",
  status: "u.status",
  deletedAt: "u.deleted_at",
};

const { clause, params } = h.buildWhereClause(
  [
    { key: "status", operation: "EQ", value: "DEACTIVATED" },
    { key: "deletedAt", operation: "NOT_NULL" },
  ],
  [],
  columnMapper,
);

const query = `DELETE FROM users${clause}`;
// query:  DELETE FROM users WHERE u.status = $1 AND u.deleted_at IS NOT NULL
// params: ['DEACTIVATED']

Low-Level Helpers

You can also import individual utilities for maximum flexibility:

const {
  createDialect,
  getKey,
  prepareWhereClause,
  prepareClause,
} = require("sql-flex-query");

const dialect = createDialect("postgres");
const mapper = { firstName: "u.first_name" };

// Resolve column names
getKey(mapper, "firstName", dialect); // 'u.first_name'
getKey(mapper, "age", dialect); // '"age"' (auto-quoted)

// Generate placeholder
dialect.placeholder(1); // '$1'
dialect.quoteIdentifier("name"); // '"name"'

// Build a single clause
const params = [];
prepareClause(
  { key: "status", operation: "EQ", value: "ACTIVE" },
  params,
  mapper,
  dialect,
);
// returns: '"status" = $1',  params: ['ACTIVE']

Extending with Custom Dialects

You can add support for custom databases by extending the BaseDialect class and registering your dialect with registerDialect().

Creating a Custom Dialect

import { BaseDialect, DialectName } from 'sql-flex-query';

class MyDialect extends BaseDialect {
  name: DialectName = 'mydialect';

  placeholder(position: number): string {
    return `:${position}`; // e.g., :1, :2
  }

  quoteIdentifier(identifier: string): string {
    return `"${identifier}"`; // double quotes
  }

  // Override if your DB has special pagination syntax
  requiresOrderByForPagination: boolean = false;
  mergesPaginationWithOrderBy: boolean = false;
  // Use default LIMIT/OFFSET or override paginationClause()
}

// Register your dialect
import { registerDialect } from 'sql-flex-query';
registerDialect('mydialect', () => new MyDialect());

// Now you can use it
const result = buildQueries({
  baseQueryTemplate: BASE,
  whereParams: [...],
  dialect: 'mydialect',
});

Using Custom Dialect Directly

You can also instantiate dialects directly without registration:

import { MyDialect } from "./my-dialect";
const dialect = new MyDialect();
const helpers = dialectHelpers(dialect); // or use dialect directly

Template Placeholders Reference

Placeholder	Required	Description
`/SELECT_COLUMNS/`	Yes	Replaced with column list or `*`
`/WHERE_CLAUSE/`	Yes	Replaced with `WHERE ...` or empty string
`/ORDER_BY/`	Yes	Replaced with `ORDER BY ...` or empty string
`/LIMIT_CLAUSE/`	Yes	Replaced with pagination clause or empty string
`/HAVING_CLAUSE/`	Optional	Replaced with `HAVING ...` (use with GROUP BY)

Operations Reference

Operation	SQL	Needs Value	Example
`EQ`	`col = ?`	Yes	`{ key: 'status', operation: 'EQ', value: 'ACTIVE' }`
`NEQ`	`col <> ?`	Yes	`{ key: 'role', operation: 'NEQ', value: 'GUEST' }`
`LIKE`	`col LIKE ?`	Yes	`{ key: 'name', operation: 'LIKE', value: '%john%' }`
`NOT_LIKE`	`col NOT LIKE ?`	Yes	`{ key: 'email', operation: 'NOT_LIKE', value: '%spam%' }`
`GT`	`col > ?`	Yes	`{ key: 'age', operation: 'GT', value: 18 }`
`LT`	`col < ?`	Yes	`{ key: 'price', operation: 'LT', value: 100 }`
`GTE`	`col >= ?`	Yes	`{ key: 'score', operation: 'GTE', value: 90 }`
`LTE`	`col <= ?`	Yes	`{ key: 'weight', operation: 'LTE', value: 80 }`
`IN`	`col IN (?, ?)`	Yes (array)	`{ key: 'status', operation: 'IN', value: ['A', 'B'] }`
`NULL`	`col IS NULL`	No	`{ key: 'deleted_at', operation: 'NULL' }`
`NOT_NULL`	`col IS NOT NULL`	No	`{ key: 'verified_at', operation: 'NOT_NULL' }`
`BETWEEN`	`col >= ? AND col < ?`	Yes (2-item array)	`{ key: 'age', operation: 'BETWEEN', value: [18, 65] }`

Demo Projects

Check out the demo repository for complete working examples:

https://github.com/ashishlohia70/sql-flex-query-demo

Community & Support

⭐ Star this repo: If you find this library useful, please give it a star on GitHub — it helps others discover it!
🐛 Report issues: Found a bug or have a feature request? Open an issue.
💬 Ask questions: Use GitHub Discussions for Q&A.
🔧 Contribute: Pull requests are welcome! See CONTRIBUTING.md for guidelines.
📖 Follow updates: Watch the repository or follow @ashishlohia70 on GitHub.

License

MIT

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sql-flex-query

Supported Databases

Why sql-flex-query?

The Problem

The Solution

Quick Comparison

Installation

Quick Start

1. Simple Query with Filters

Basic Examples

1. Simple SELECT with WHERE and Pagination

2. BETWEEN — Range Filtering

3. Text Search (OR) + Filters (AND)

Complex Examples

4. Multi-table JOIN with Column Mapping

5. GROUP BY + HAVING (Aggregation Reports)

6. GROUP BY with modifyCountQuery

7. LEFT JOIN + DISTINCT (Fluent API)

8. Sales Dashboard (Fluent API + GROUP BY + HAVING + MSSQL)

9. Subquery JOIN with MySQL (Fluent API)

Dialect Helpers for INSERT / UPDATE / DELETE

10. INSERT Query (Postgres)

11. UPDATE Query with WHERE (Postgres & MSSQL)

12. DELETE Query with WHERE (Postgres)

Low-Level Helpers

Extending with Custom Dialects

Creating a Custom Dialect

Using Custom Dialect Directly

Template Placeholders Reference

Operations Reference

Demo Projects

Community & Support

License

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