diff --git a/backend/lib/Model/Entity.php b/backend/lib/Model/Entity.php
index da209bd..130b256 100644
--- a/backend/lib/Model/Entity.php
+++ b/backend/lib/Model/Entity.php
@@ -65,7 +65,7 @@ abstract class Entity {
 
 	/**
 	 * @OneToMany(targetEntity="Property", mappedBy="entity", cascade={"remove", "persist"})
-	 * @OrderBy({"key" = "ASC"})
+	 * @OrderBy({"`key`" = "ASC"})
 	 */
 	protected $properties = NULL;
 
diff --git a/backend/lib/Model/Property.php b/backend/lib/Model/Property.php
index 8fdb9ad..fc72041 100644
--- a/backend/lib/Model/Property.php
+++ b/backend/lib/Model/Property.php
@@ -36,7 +36,7 @@ use Volkszaehler\Model;
  * @Table(
  * 		name="properties",
  * 		uniqueConstraints={
- * 			@UniqueConstraint(name="unique_keys", columns={"entity_id", "`key`	"})
+ * 			@UniqueConstraint(name="unique_keys", columns={"entity_id", "`key`"})
  * 		}
  * )
  * @HasLifecycleCallbacks
diff --git a/share/sql/mysql.sql b/share/sql/mysql.sql
index 546e840..e06bba4 100644
--- a/share/sql/mysql.sql
+++ b/share/sql/mysql.sql
@@ -1,9 +1,9 @@
 CREATE TABLE entities (id SMALLINT AUTO_INCREMENT NOT NULL, uuid VARCHAR(36) NOT NULL, type VARCHAR(255) NOT NULL, class VARCHAR(255) NOT NULL, UNIQUE INDEX entities_uuid_uniq (uuid), PRIMARY KEY(id)) ENGINE = InnoDB;
 CREATE TABLE groups_channel (group_id SMALLINT NOT NULL, channel_id SMALLINT NOT NULL, PRIMARY KEY(group_id, channel_id)) ENGINE = InnoDB;
 CREATE TABLE groups_groups (parent_id SMALLINT NOT NULL, child_id SMALLINT NOT NULL, PRIMARY KEY(parent_id, child_id)) ENGINE = InnoDB;
-CREATE TABLE data (id SMALLINT AUTO_INCREMENT NOT NULL, channel_id SMALLINT DEFAULT NULL, timestamp BIGINT NOT NULL, value NUMERIC(5, 2) NOT NULL, PRIMARY KEY(id)) ENGINE = InnoDB;
+CREATE TABLE data (id SMALLINT AUTO_INCREMENT NOT NULL, channel_id SMALLINT DEFAULT NULL, timestamp BIGINT NOT NULL, value NUMERIC(5, 2) NOT NULL, UNIQUE INDEX unique_timestamp (timestamp, channel_id), PRIMARY KEY(id)) ENGINE = InnoDB;
 CREATE TABLE tokens (id SMALLINT AUTO_INCREMENT NOT NULL, entity_id SMALLINT DEFAULT NULL, token VARCHAR(255) NOT NULL, valid BIGINT NOT NULL, UNIQUE INDEX tokens_token_uniq (token), PRIMARY KEY(id)) ENGINE = InnoDB;
-CREATE TABLE properties (id SMALLINT AUTO_INCREMENT NOT NULL, entity_id SMALLINT DEFAULT NULL, name VARCHAR(255) NOT NULL, value VARCHAR(255) NOT NULL, UNIQUE INDEX unique_properties (id, name), PRIMARY KEY(id)) ENGINE = InnoDB;
+CREATE TABLE properties (id SMALLINT AUTO_INCREMENT NOT NULL, entity_id SMALLINT DEFAULT NULL, `key` VARCHAR(255) NOT NULL, value VARCHAR(255) NOT NULL, UNIQUE INDEX unique_keys (entity_id, `key`), PRIMARY KEY(id)) ENGINE = InnoDB;
 ALTER TABLE groups_channel ADD FOREIGN KEY (group_id) REFERENCES entities(id);
 ALTER TABLE groups_channel ADD FOREIGN KEY (channel_id) REFERENCES entities(id);
 ALTER TABLE groups_groups ADD FOREIGN KEY (parent_id) REFERENCES entities(id);