使用情景: 数据库

DDL(Data Definition Language)数据定义语言

数据库和表的操作都属于ddl, 比如: Create、Drop和Alter,
DDL所站的高度, 最低也比记录高一层

创建或打开数据库

const TableName = "IMGDATA"; // 表名: IMGDATA // 字段1 id 整数 主键 自增 // 字段2 name 字符串 不可为空 // 字段3 img BLOB let db = sqlite.open(   "./data.db",   { version: 1 },   {     onOpen: function (db) {       db.execSQL(         "CREATE TABLE IF NOT EXISTS " +           TableName +           "(" +           "`id` INTEGER PRIMARY KEY AUTOINCREMENT, " +           "`name` TEXT NOT NULL UNIQUE, " +           "`img` BLOB" +           ")"       );     },   } ); 

关闭数据库

db.close(); 

打印所有表

let db = sqlite.open("./data.db"); log("数据库所有表的信息: ", db.rawQuery("SELECT * FROM sqlite_master WHERE type='table'", null).all()); 

删除表

const TableName = "IMGDATA"; let db = sqlite.open(   "./data.db",   { version: 1 },   {     onOpen: function (db) {       db.execSQL("drop TABLE " + TableName);     },   } ); 

DML(Data Manipulation Language 数据操控语言)

操作的单位是记录, 增删改查都属于dml, 操作的单位是记录

增加

let img = images.read(files.join(files.getSdcardPath(), "test.jpg")); let r = db.insert(TableName, {   name: "test",   img: img, }); log(r); 

删除

log("删除name的值为test的记录: ", db.delete(TableName, "name = 'test'", null)); 

修改

// 修改符合条件name=test的记录, 字段name的改为测试 log("修改: ", db.update(TableName, { name: "测试" }, "name = ?", ["test"])); log("修改后: ", db.rawQuery("SELECT * FROM " + TableName + " WHERE name = ?", ["测试"]).single()); 

查询

log("所有数据: ", db.rawQuery("SELECT * FROM " + TableName, null).all()); log("第一个数据: ", db.rawQuery("SELECT * FROM " + TableName, null).single()); 

条件查询

log("条件查询: ", db.rawQuery("SELECT * FROM " + TableName + " WHERE name = ?", ["测试"]).single()); 

事务

const TableName = "IMGDATA"; let db = sqlite.open("./data.db"); db.transaction(function () {   db.update(TableName, { name: "测试改名字" }, "name = '测试'", null); })   .on("begin", function (t) {     log("事务开始: ", t);   })   .on("commit", function (t) {     log("事务完成: ", t);   })   .on("rollback", function (t) {     log("事务回滚: ", t);   })   .on("end", function (t) {     log("事务结束: ", t);   })   .on("error", function (e) {     console.error(e);   }); db.close();