之前没记录更新的操作，今天有空记录一下mongodb update的使用

先看语法：

db.collection.update( <query>, <update>, <options> )

语法很简单，但是使用起来，要配合一些函数，就会复杂一些，解释一下

query：条件限定，也就是需要更新行的条件，相当于SQL中where后面的条件判断

update：相当于SQL表中的set语句

options：这里需要注意的是mongodb的更新操作，默认只更新符合条件的第一行，如果要更新符合条件的所有行，需要指定multi为true，还有一个一个参数是upsert，意思是如果不存在符合query的记录，插入update的数据，默认是false不插入，可以指定true

 最简单的一个例子，大家看一下：

PRIMARY> db.test.save({id:1,"name":"hank"})
PRIMARY> db.test.find()
{ "_id" : ObjectId("50c055656b41f59a0235881b"), "id" : 1, "name" : "hank" }
PRIMARY> db.test.update({id:1},{"name":"dazuiba"})
PRIMARY> db.test.find()
{ "_id" : ObjectId("50c055656b41f59a0235881b"), "name" : "dazuiba" }

默认更新一行例子：

PRIMARY> db.test.find()
{ "_id" : ObjectId("50c056876b41f59a0235881c"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c056886b41f59a0235881d"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c056896b41f59a0235881e"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c0568a6b41f59a0235881f"), "id" : 1, "name" : "hank" }
PRIMARY>  db.test.update({id:1},{"name":"dazuiba"})
PRIMARY>  db.test.find()
{ "_id" : ObjectId("50c056876b41f59a0235881c"), "name" : "dazuiba" }
{ "_id" : ObjectId("50c056886b41f59a0235881d"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c056896b41f59a0235881e"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c0568a6b41f59a0235881f"), "id" : 1, "name" : "hank" }

更新所有符合条件的行：

PRIMARY> db.test.find()
{ "_id" : ObjectId("50c056e46b41f59a02358820"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c056e56b41f59a02358821"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c056e66b41f59a02358822"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c056e86b41f59a02358823"), "id" : 1, "name" : "hank" }
PRIMARY> db.test.update({id:1},{"name":"dazuiba"},false,true)   --报错，大家注意一下这里，需要$相关的操作
multi update only works with $ operators
PRIMARY> db.test.update({id:1},{$set:{"name":"dazuiba"}},false,true)
PRIMARY> db.test.find()
{ "_id" : ObjectId("50c056e46b41f59a02358820"), "id" : 1, "name" : "dazuiba" }
{ "_id" : ObjectId("50c056e56b41f59a02358821"), "id" : 1, "name" : "dazuiba" }
{ "_id" : ObjectId("50c056e66b41f59a02358822"), "id" : 1, "name" : "dazuiba" }
{ "_id" : ObjectId("50c056e86b41f59a02358823"), "id" : 1, "name" : "dazuiba" }

更新不存在的行，如果不存在，那么插入进去：

PRIMARY> db.test.find()
{ "_id" : ObjectId("50c058256b41f59a02358828"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c058266b41f59a02358829"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c058266b41f59a0235882a"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c058276b41f59a0235882b"), "id" : 1, "name" : "hank" }
PRIMARY> db.test.update({id:2},{$set:{"name":"dazuiba"}},true,false)
PRIMARY> db.test.find()
{ "_id" : ObjectId("50c058256b41f59a02358828"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c058266b41f59a02358829"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c058266b41f59a0235882a"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c058276b41f59a0235882b"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c05840638c411993e87a5c"), "id" : 2, "name" : "dazuiba" }

只要理解了2个参数意思，灵活使用即可，以下是几个例子

PRIMARY> db.test.find()
{ "_id" : ObjectId("50c0589e6b41f59a0235882c"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c058a06b41f59a0235882d"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c058a16b41f59a0235882e"), "id" : 1, "name" : "hank" }
{ "_id" : ObjectId("50c058a16b41f59a0235882f"), "id" : 1, "name" : "hank" }
PRIMARY> db.test.update({id:1},{$set:{"name":"dazuiba"}},true,true)
PRIMARY> db.test.find()
{ "_id" : ObjectId("50c0589e6b41f59a0235882c"), "id" : 1, "name" : "dazuiba" }
{ "_id" : ObjectId("50c058a06b41f59a0235882d"), "id" : 1, "name" : "dazuiba" }
{ "_id" : ObjectId("50c058a16b41f59a0235882e"), "id" : 1, "name" : "dazuiba" }
{ "_id" : ObjectId("50c058a16b41f59a0235882f"), "id" : 1, "name" : "dazuiba" }
PRIMARY> db.test.update({id:2},{$set:{"name":"hank"}},true,true)
PRIMARY>  db.test.find()
{ "_id" : ObjectId("50c0589e6b41f59a0235882c"), "id" : 1, "name" : "dazuiba" }
{ "_id" : ObjectId("50c058a06b41f59a0235882d"), "id" : 1, "name" : "dazuiba" }
{ "_id" : ObjectId("50c058a16b41f59a0235882e"), "id" : 1, "name" : "dazuiba" }
{ "_id" : ObjectId("50c058a16b41f59a0235882f"), "id" : 1, "name" : "dazuiba" }
{ "_id" : ObjectId("50c058ea638c411993e87a5d"), "id" : 2, "name" : "hank" }

$相关操作下一次介绍