feat: Support for nested sql statements

[skyjur]

I think nested query statements gives much better readability compared to appends:

Let' say I have helpers

function authorFilter(author) {
  return SQL`author=${author}`;
}
function nameFilter(name) {
  return SQL`name=${name}`;
}

With append it would be:

SQL`SELECT author FROM books WHERE `
   .append(authorFilter(author))
   .append(' AND ')
   .append(nameFilter(book))`

With nested queries:

SQL`SELECT author FROM books WHERE
     ${authorFilter(author)} AND
     ${nameFilter(book)}`;

This also enables easy support for raw values:

const tableName = "books";

SQL`SELECT * FROM ${SQL([tableName])}`.sql;
// => SELECT * FROM books

However SQL( [ value ] ) syntax is slightly cryptic. I'd vote to bring back raw() as

SQL.raw = function(value) {
  return SQL([value]);
};

Or this:

function SQL(strings) {
   if(typeof strings === 'string') {
       return SQL([strings])
   else
  return new SQLStatement(strings.slice(0), Array.from(arguments).slice(1))
}

SQL`SELECT * FROM ${SQL(tableName)}`

This also solves use case described in https://github.com/felixfbecker/node-sql-template-strings/pull/72

[codecov[bot]]

Codecov Report

Merging #79 into master will not change coverage. The diff coverage is 100%.

@@          Coverage Diff          @@
##           master    #79   +/-   ##
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  Coverage     100%   100%           
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  Files           1      1           
  Lines          35     45   +10     
  Branches        6      7    +1     
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+ Hits           35     45   +10

Impacted Files	Coverage Δ
index.js	100% <100%> (ø)	:arrow_up:

[KeKs0r]

@skyjur Is this PR still in development? If you are busy I am more than happy to help out. Really looking forward to that feature :)

[skyjur]

@KeKs0r it's kind of ready and I've used it in a few simple cases, but haven't done very extensive testing.

[lucleray]

@skyjur I love the idea of nested sql statements for so I implemented it in @sequencework/sql (which is shamelessly inspired by sql-template-strings). I'd love if you could try it and let me know what you think 😬