HarmonyOs development: relational database package of add, delete, change and check

Less persistent data storage, we can choose user preferences or distributed key-value database for operation, if the first two can not be met, in Hongmeng, also gives us a relational database for the operation of the data between the operation, and Android is similar to a relational database based on the SQLite component, provides a complete set of mechanisms for the management of local databases, but also External to provide a series of add, delete, change, check and other interfaces, very convenient, in order to more convenient operation of the data, the current system Api made a simple layer of encapsulation.

 The content of this post is roughly as follows:

 1. Remote address dependency

 2, database creation and table creation

 3. Database additions, deletions and changes

 4. Summary of use

 I. Remote address dependency

Set up the three-way package dependency in oh-package.json5 of the project module with the following configuration example:

"dependencies": { "@abner/datastore": "^1.0.0"}

 II. Database creation and table creation

 1. Database creation

The database is created, by default, during initialization, just initialize it in AbilityStage.

DbUtil.getInstance().init(this.context)

 Attributes

storeConfig

 2、Data table creation

Data tables are created in two ways, either by sql statement execution or by object form execution.

 sql statement execution

DbUtil.getInstance()
          .executeSql("CREATE TABLE table_name(id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(50),age INT)")

 Object form implementation [recommended

object form, weakened the sql statement, but itself is still in the form of sql to create a data table, just the business layer of the operation, no sql operation, the implementation is very simple and intuitive, the first parameter is the name of the data table that is table_name, the second parameter is an object, that is, the fields of the data table, each field, you need to specify the data type and other necessary parameters, such as primary key, self incremental length, etc.. For example, the primary key, self-incrementing, length and so on.

DbUtil.getInstance().createTable("table_name", {
    "id": { type: DbTableFieldType.INTEGER, isPrimaryKey: true, isAutoIncrement: true },
     "name": { type: DbTableFieldType.VARCHAR, length: 120 },
     "age": { type: DbTableFieldType.INT, length: 30 }
})

 III. Database additions, deletions and changes

1、Add

 General Storage

 A ValuesBucket object needs to be defined for passing.

const valueBucket1: ValuesBucket = {
          'name': "AbnerMing",
          'age': 18,
        }
DbUtil.getInstance().insert("table_name", valueBucket1)

 object storage

 let bean = new DbDataBean()
 bean.name = "AbnerMing"
 bean.age = 18
 DbUtil.getInstance().insertBean("table_name", bean)

2、Delete

 Ordinary deletion

You need to use RdbPredicates object to set the filter conditions, you can just check the official website Api.

let deleteRdbPredicates = new relationalStore.RdbPredicates("table_name");
deleteRdbPredicates.equalTo("id", 1);

DbUtil.getInstance().delete(deleteRdbPredicates)

 Object Deletion

Similar to normal deletion, except that the RdbPredicates object is simply encapsulated, and you need to call the filterRdbPredicates method to set the filter conditions.

DbUtil.getInstance()
          .filterRdbPredicates({ equalTo: { "id": 2 } })
          .deleteBean("table_name")

3、Change

 General Modifications

const valueBucket: ValuesBucket = {
          'name': "ming",
          'age': 28,
        }

let upDataRdbPredicates = new relationalStore.RdbPredicates("table_name");
upDataRdbPredicates.equalTo("id", 1)

DbUtil.getInstance().update(upDataRdbPredicates, valueBucket)

 Object Modification

The filterRdbPredicates method is the filter condition, i.e. which data you want to change.

 let uBean = new DbDataBean()
 uBean.name = "Ming"
 uBean.age = 20
 DbUtil.getInstance()
  .filterRdbPredicates({ equalTo: { "id": 2 } })
  .updateBean("table_name", uBean)

4、Find

 general inquiry

let predicates = new relationalStore.RdbPredicates("table_name");

 DbUtil.getInstance().query(predicates, (resultSet: relationalStore.ResultSet) => {

          while (resultSet.goToNextRow()) {
            const id = resultSet.getLong(resultSet.getColumnIndex("id"));
            const name = resultSet.getString(resultSet.getColumnIndex("name"));
            const age = resultSet.getLong(resultSet.getColumnIndex("age"));
          }
        })

 object search

 Get All

DbUtil.getInstance()
          .queryAllBean<DbDataBean>("table_name", (data) => {
           
          })

 Get a single

DbUtil.getInstance()
          .filterRdbPredicates({ equalTo: { "id": 1 } })
          .queryBean<DbDataBean>("table_name", (data) => {
            
          })

 IV. Summary of use

Each method is reserved for a variety of invocation methods, such as the use of callback asynchronous callback or the use of Promise asynchronous callback , or synchronous execution , we can use the process , according to their own business needs for selective calls , but also exposed the success and failure of the method , you can target to determine the execution process in the implementation of the implementation of the success or not.

 The following case:

DbUtil.getInstance().delete(deleteRdbPredicates,
          (rows: number)=>{

          },
          (err: BusinessError)=>{

        })