id text pid

1 My Documents 0
2 photos 1
3 Friend 2
4 Wife 2
5 Company 2
6 Program Files 1
7 Intel 6
8 Java 6

数据库中是以上结构，如何写段代码生成如下结构的json数据？

[{

"id":1,
"text":"My Documents",
"children":[{
    "id":2,
    "text":"Photos",
    "children":[{
        "id":3,
        "text":"Friend"
    },{
        "id":4,
        "text":"Wife"
    },{
        "id":5,
        "text":"Company"
    }]
},{
    "id":6,
    "text":"Program Files",
    "children":[{
        "id":7,
        "text":"Intel"
    },{
        "id":8,
        "text":"Java",
    }]
}]

}]