Select API - Medoo

Version: v2.4.0

select

Retrieve data from a table.

select($table, $columns)

table [string]
The name of the table to query.
columns [array/string]
The column or columns to retrieve.

select($table, $columns, $where)

table [string]
The name of the table to query.
columns [array/string]
The column or columns to retrieve.
where [array] (optional)
The WHERE clause used to filter the result set.

select($table, $join, $columns, $where)

table [string]
The name of the table to query.
join [array]
The join definitions used to combine related tables. Omit this parameter if no joins are required.
columns [array/string]
The column or columns to retrieve.
where [array] (optional)
The WHERE clause used to filter the result set.

Return Value

[array] An array containing the retrieved rows.

You can use * for the columns parameter to retrieve all columns. However, explicitly specifying only the required columns is recommended for better performance and readability.

$data = $database->select("account", [
	"user_name",
	"email"
], [
	"user_id[>]" => 100
]);

// Example result:
// array(
//  [0] => array(
//	  "user_name" => "foo",
//	  "email" => "foo@bar.com"
//  ),
//  [1] => array(
//	  "user_name" => "cat",
//	  "email" => "cat@dog.com"
//  )
// )

foreach ($data as $item) {
	echo "User: " . $item["user_name"] . " - Email: " . $item["email"] . "<br/>";
}

// Select all columns.
$data = $database->select("account", "*");

// Select a single column.
$data = $database->select("account", "user_name");

// Example result:
// array(
//  [0] => "foo",
//  [1] => "cat"
// )

Fetching Rows with a Callback

By default, select() loads the full result set into memory and returns it as an array.

When retrieving a large number of rows, this can increase memory usage significantly. If you pass a callback such as function ($data) {} as the last argument to select(), Medoo will fetch and process each row immediately instead of storing the entire result set in memory first.

This approach is more memory-efficient when working with large datasets.

$database->select("account", ["name"], function ($data) {
	echo $data["name"];
});

$database->select("account", [
	"name"
], function ($data) {
	echo $data["name"];
});

Performance Benchmark

The following example compares memory usage when fetching and outputting 1,000, 5,000, and 20,000 rows from a MySQL database. Memory usage is measured with memory_get_usage().

// Method 1
$database->select("account", ["name"], function ($data) {
	echo $data["name"];
});

// Compare with:

// Method 2
$data = $database->select("account", ["name"]);

foreach ($data as $item) {
	echo $item["name"];
}

	Method 1	Method 2
1,000 Records	789 KB	1.2 MB
5,000 Records	1.1 MB	3.3 MB
20,000 Records	2.26 MB	11.1 MB

Table Joins

SQL JOIN clauses combine rows from multiple tables. Medoo provides a simple syntax for building joins.

[>] ==> LEFT JOIN
[<] ==> RIGHT JOIN
[<>] ==> FULL JOIN
[><] ==> INNER JOIN

$database->select("post", [
	// Define the relationship between the main table and the joined table.
	"[>]account" => ["author_id" => "user_id"]
], [
	"post.title",
	"account.city"
]);

The column author_id in the post table is matched to the column user_id in the account table.

"[>]account" => ["author_id" => "user_id"]

LEFT JOIN "account" ON "post"."author_id" = "account"."user_id"

If both tables use the same column name, you can use the shorthand form.

"[>]album" => "user_id"

LEFT JOIN "album" USING ("user_id")

If multiple columns share the same names in both tables, you can pass them as an array.

"[>]photo" => ["user_id", "avatar_id"]

LEFT JOIN "photo" USING ("user_id", "avatar_id")

If you need to join the same table more than once, assign an alias to the joined table.

"[>]account (replier)" => ["replier_id" => "user_id"]

LEFT JOIN "account" AS "replier" ON "post"."replier_id" = "replier"."user_id"

You can also reference a previously joined table by prefixing the column with the table name.

"[>]account" => ["author_id" => "user_id"],
"[>]album" => ["account.user_id" => "user_id"]

LEFT JOIN "account" ON "post"."author_id" = "account"."user_id"
LEFT JOIN "album" ON "account"."user_id" = "album"."user_id"

Multiple JOIN Conditions

"[>]account" => [
	"author_id" => "user_id",
	"album.user_id" => "user_id"
]

LEFT JOIN "account" ON
"post"."author_id" = "account"."user_id" AND
"album"."user_id" = "account"."user_id"

Additional JOIN Conditions

You can also add logical conditions to the join clause.

"[>]comment" => [
	"author_id" => "user_id",
	"AND" => [
		"rate[>]" => 50
	]
]

LEFT JOIN "comment" ON "post"."author_id" = "comment"."user_id" AND "rate" > 50

Join with a Raw Object

"[>]account" => Medoo::raw("ON <post.author_id> = <account.user_id>")

LEFT JOIN "account" ON "post"."author_id" = "account"."user_id"

Data Mapping

You can customize the structure of the returned data. The mapping key does not need to match the original column name, and nested output is supported.

$data = $database->select("post", [
	"[>]account" => ["user_id"]
], [
	"post.content",

	"userData" => [
		"account.user_id",
		"account.email",

		"meta" => [
			"account.location",
			"account.gender"
		]
	]
], [
	"LIMIT" => [0, 2]
]);

echo json_encode($data);

[
	{
		"content": "Hello world!",
		"userData": {
			"user_id": "1",
			"email": "foo@example.com",
			"meta": {
				"location": "New York",
				"gender": "male"
			}
		}
	},
	{
		"content": "Hey everyone",
		"userData": {
			"user_id": "2",
			"email": "bar@example.com",
			"meta": {
				"location": "London",
				"gender": "female"
			}
		}
	}
]

Index Mapping

If you use a column name as the first key in the column definition, the result will be indexed by that column.

$data = $database->select("post", [
	"user_id" => [
		"nickname",
		"location",
		"email"
	]
]);

{
	"10": {
		"nickname": "foo",
		"location": "New York",
		"email": "foo@example.com"
	},
	"12": {
		"nickname": "bar",
		"location": "New York",
		"email": "bar@medoo.in"
	}
}

Data Type Declarations

You can explicitly declare the output type for selected fields.

// Supported data types: [String | Bool | Int | Number | Object | JSON]
// [String] is the default type for all output values.
// [Object] represents PHP data serialized with serialize() and decoded with unserialize().
// [JSON] represents valid JSON data and will be decoded with json_decode().

$data = $database->select("post", [
	"[>]account" => ["user_id"]
], [
	"post.post_id",

	"profile" => [
		"account.age [Int]",
		"account.is_locked [Bool]",
		"account.userData [JSON]"
	]
]);

echo json_encode($data);

[
	{
		"post_id": "1",
		"profile": {
			"age": 20,
			"is_locked": true,
			"userData": ["foo", "bar", "tim"]
		}
	},
	{
		"post_id": "2",
		"profile": {
			"age": 25,
			"is_locked": false,
			"userData": ["mydata1", "mydata2"]
		}
	}
]

// Store an object in the database, and retrieve it later.
class Foo {
	var $bar = "cat";

	public function __wakeup()
	{
		$this->bar = "dog";
	}
}

$object_data = new Foo();

$database->insert("account", [
	"data" => $object_data
]);

$data = $database->select("account", [
	"data [Object]"
]);

echo $data[0]["data"]->bar;

// The object\'s __wakeup() method is called during unserialize().
// Therefore, the output is "dog".

Aliases

You can assign an alias to a column or table name. This is especially useful in joined queries to avoid name conflicts or make the output clearer.

$data = $database->select("account", [
	"user_id",
	"nickname (my_nickname)"
]);

// Example result:
// array(
//  [0] => array(
//	  "user_id" => "1",
//	  "my_nickname" => "foo"
//  ),
//  [1] => array(
//	  "user_id" => "2",
//	  "my_nickname" => "bar"
//  )
// )

$data = $database->select("post (content)", [
	"[>]account (user)" => "user_id",
], [
	"content.user_id (author_id)",
	"user.user_id"
]);

// Example result:
// array(
//  [0] => array(
//	  "author_id" => "1",
//	  "user_id" => "321"
//  ),
//  [1] => array(
//	  "author_id" => "2",
//	  "user_id" => "322"
//  )
// )

SELECT
	"content"."user_id" AS "author_id",
	"user"."user_id"
FROM
	"post" AS "content"
LEFT JOIN "account" AS "user" USING ("user_id")

DISTINCT

To add the DISTINCT keyword to a selected column, prefix the column name with @.

$data = $database->select("account", [
	// DISTINCT will be applied to this column.
	"@location",
	
	"id",
	"name",
]);

SELECT DISTINCT "location", "id", "name"
FROM "account"

To count distinct values, use a raw expression.

$data = $database->select("account", [
	"unique_locations" => Medoo::raw("COUNT(DISTINCT <location>)")
]);

SELECT COUNT(DISTINCT "location") AS "unique_locations"
FROM "account"

select

table [string]

columns [array/string]

table [string]

columns [array/string]

where [array] (optional)

table [string]

join [array]

columns [array/string]

where [array] (optional)

Return Value

Fetching Rows with a Callback

Performance Benchmark

Table Joins

Multiple JOIN Conditions

Additional JOIN Conditions

Join with a Raw Object

Data Mapping

Index Mapping

Data Type Declarations

Aliases

DISTINCT