Waddler SQL append

This guide assumes familiarity with:

Quick start with Waddler - read here
Waddler SQL template - read here
sql.identifier - read here
sql.raw - read here

sql.append lets you conveniently append SQL templates:

const query = sql`select * from users where id = 10`;
query.append(sql` or id = 20`);

const result = await query;

select * from users where id = 10 or id = 20;

It is an extremely useful API to build dynamic queries:

type Filter = {
  key: string,
  operator: "=" | "!=", 
  value: string,
}

const listItems = async (params: {limit: number, offset?: number, filter?: Filter }) => {
  const query = sql`select * from items`;

  if(filter) {
    query.append(sql` where ${sql.identifier(it.key)} ${sql.raw(it.operator)} ${it.value}`)
  }

  query.append(sql` limit ${params.limit}`);

  if(params.offset) {
    query.append(sql` offset ${params.offset}`);
  }
}

await listItems({ limit: 50 });
await listItems({ limit: 50, filter: { key: "name", operator: "=", value: "Item 1"}});
await listItems({ limit: 50, offset: 50, filter: { key: "name", operator: "=", value: "Item 1"}});

select * from items limit $1; -- [50] params
select * from items where "name" = $1 limit $2; -- ["Item 1", 50] params
select * from items where "name" = $1 limit $2 offset $3; -- ["Item 1", 50, 50] params