Initial SQLite development (#1)

Reviewed-on: #1

src/Query/Exists.php

@@ -0,0 +1,47 @@
+<?php declare(strict_types=1);
+
+namespace BitBadger\PDODocument\Query;
+
+use BitBadger\PDODocument\{Field, Query};
+
+/**
+ * Queries to determine document existence
+ */
+class Exists
+{
+    /**
+     * The shell of a query for an existence check
+     *
+     * @param string $tableName The name of the table in which existence should be checked
+     * @param string $whereClause The conditions for which existence should be checked
+     * @return string The query to determine existence of documents
+     */
+    public static function query(string $tableName, string $whereClause): string
+    {
+        return "SELECT EXISTS (SELECT 1 FROM $tableName WHERE $whereClause)";
+    }
+
+    /**
+     * Query to determine if a document exists for the given ID
+     *
+     * @param string $tableName The name of the table in which document existence should be checked
+     * @return string The query to determine document existence by ID
+     */
+    public static function byId(string $tableName): string
+    {
+        return self::query($tableName, Query::whereById());
+    }
+
+    /**
+     * Query to determine if documents exist using a comparison on JSON fields
+     *
+     * @param string $tableName The name of the table in which document existence should be checked
+     * @param Field[] $fields The field comparison to match
+     * @param string $conjunction How to handle multiple conditions (optional; defaults to `AND`)
+     * @return string The query to determine document existence by field comparison
+     */
+    public static function byFields(string $tableName, array $fields, string $conjunction = 'AND'): string
+    {
+        return self::query($tableName, Query::whereByFields($fields, $conjunction));
+    }
+}