ES6 tagged template strings for SQL

I love sql-template-strings, except for one thing. Immutablility. There were a number of discussions about adding it, either via a .concat method, or by allowing nesting templates.

Personally I like both approaches. so used both

• nested querys: the inner queries are copied, not mutated.
• .append will copy the arguments, not mutate, but will mutate the original query.
• .concat will copy the arguments, not mutate and will not mutate the original query returning a new object.

Otherwise the API is similar, the sql, raw method both produce an SQLStatement, which has (apart from the properties and methods required for actually making the queries) the following properties:

• .concat(...next: Array<SQLStatement|string>): SQLStatement concatenates all the queries together in order, producing a new statement.
• .concat(s: TemplateStringArray, v: any[]): SQLStatement the tagged template string version of concatenate, but of course can only work on a single input.
• .append(...next: Array<SQLStatement|string>): SQLStatement like concatenate, but mutates the query it is called on.
• .append(s: TemplateStringArray, v: any[]): SQLStatement the tagged template string version of the append.
• .clone() explicit copy of the statement - note that the values array is shallow copied.

NB I have not implemented the bind syntax yet. I plan to at some point but have no need for it yet.

There are also some useful helper functions:

• join(separator: string, arr: Array<Statement | string | number>): Statement: joins the statements together in order, using the given seprator (note that spaces between statements will be added as needed).
• mapJoin<T>(separator: string, arr: Array<T>, fn: (v: T, i: number, a: Array<T>) => Statement | string | number): Statement: the same as join but allows you to pass an array of anything, and a mapping function to produce a Statement or primitive.
• like(str: string): string: escapes a string for a SQL LIKE clause. It wraps _,%,[,] in square brackets. This may or may not be enough in your SQL server.

This allows you to do things like:

import { sql, mapJoin, like } from "@proc/sql";

// like a database response...
const bigArrayOfThings = [{ id: 1, name: "Alice" }, { id: 2, name: "Bob" }];

// find articles with all the names in (simplistic search)
const query = sql`
  SELECT title, body
  FROM articles
  WHERE ${mapJoin("AND", bigArrayOfThings, ({ id }) => {
    // create a LIKE clause
    const matcher = `%${like(id)}%`;
    sql`body LIKE ${matcher}`;
  })};
`;