Add sql query builder

src/QueryBuilder/Column.php

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+<?php
+
+
+namespace TipsTricks\QueryBuilder;
+
+
+class Column
+{
+    private $expression;
+    private $alias;
+
+    public function __construct(string $expression, string $alias = null)
+    {
+        $this->expression = $expression;
+        $this->alias = $alias;
+    }
+
+    public function __toString()
+    {
+        if ($this->alias) {
+            return Query::INDENT . $this->expression . ' AS ' . $this->alias;
+        }
+        return Query::INDENT . $this->expression;
+    }
+}

src/QueryBuilder/From.php

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+<?php
+
+
+namespace TipsTricks\QueryBuilder;
+
+
+class From
+{
+    private $expression;
+
+    public function __construct(string $expression)
+    {
+        $this->expression = $expression;
+    }
+
+    public function __toString()
+    {
+        return "FROM " . $this->expression . PHP_EOL;
+    }
+}

src/QueryBuilder/Join.php

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+<?php
+
+
+namespace TipsTricks\QueryBuilder;
+
+
+class Join
+{
+    private $table;
+
+    private $condition;
+
+    public function __construct($table)
+    {
+        $this->table = $table;
+    }
+
+    private function conditions() {
+        return " ON order.customer_id = customer.id";
+    }
+
+    public function __toString()
+    {
+        return Query::INDENT . "JOIN " . $this->table . $this->conditions();
+    }
+}

src/QueryBuilder/Query.php

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+<?php
+
+namespace TipsTricks\QueryBuilder;
+
+class Query
+{
+    const INDENT = "    ";
+
+    const FINAL_POINT = ";";
+
+    private $select;
+    private $from;
+    private $where;
+
+    public function __construct(Select $select, From $from, Where $where)
+    {
+        $this->select = $select;
+        $this->from   = $from;
+        $this->where  = $where;
+    }
+
+    public function __toString()
+    {
+        $parts = [
+            $this->select,
+            $this->from(),
+            $this->where,
+            Query::FINAL_POINT,
+        ];
+
+        return implode("\n", $parts);
+    }
+
+    private function from()
+    {
+        return $this->from . (new Join('customer'));
+    }
+}
+

src/QueryBuilder/Select.php

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+<?php
+
+namespace TipsTricks\QueryBuilder;
+
+class Select
+{
+    private $columns;
+
+    public function __construct(array $columns)
+    {
+        $this->columns = $columns;
+    }
+
+    public function __toString()
+    {
+        $select = implode(",\n", $this->columns);
+        return PHP_EOL . "SELECT" . PHP_EOL . $select;
+    }
+}

src/QueryBuilder/Where.php

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+<?php
+
+
+namespace TipsTricks\QueryBuilder;
+
+
+class Where
+{
+    public function __toString()
+    {
+        return "WHERE " . new WhereEquals('customer.id', '14');
+    }
+}

src/QueryBuilder/WhereEquals.php

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+<?php
+
+
+namespace TipsTricks\QueryBuilder;
+
+
+class WhereEquals
+{
+    private $one;
+    private $two;
+
+    public function __construct($one, $two)
+    {
+        $this->one = $one;
+        $this->two = $two;
+    }
+
+    public function __toString()
+    {
+        return $this->one . ' = ' . $this->two;
+    }
+}

tests/QueryBuilder/QueryTest.php

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+<?php
+
+use TipsTricks\QueryBuilder\Column;
+use TipsTricks\QueryBuilder\From;
+use TipsTricks\QueryBuilder\Query;
+use TipsTricks\QueryBuilder\Select;
+use TipsTricks\QueryBuilder\Where;
+
+class QueryTest extends \PHPUnit\Framework\TestCase
+{
+    public function testQuery()
+    {
+        $selects = [
+            new Column("SUM(order.price)", "total"),
+            new Column("customer.name"),
+        ];
+
+        $from = new From('order');
+
+        $select = new Select($selects);
+
+        $where = new Where();
+        $query = new Query($select, $from, $where);
+
+        $sql = <<<SQL
+
+SELECT
+    SUM(order.price) AS total,
+    customer.name
+FROM order
+    JOIN customer ON order.customer_id = customer.id
+WHERE customer.id = 14
+;
+SQL;
+         self::assertSame($sql, (string) $query);
+    }
+}