在开发中，我们也会遇到在离线状态的情况下对数据进行存储；我们常用的有session、localstroage等操作；但是存储大小都是有限制的；因此前端可以使用sqlite对数据库的数据进行存储；
sqlite数据库简介：SQLite，是一款轻型的数据库，是遵守ACID的关系型数据库管理系统，它包含在一个相对小的C库中。它是D.RichardHipp建立的公有领域项目。它的设计目标是嵌入式的，而且已经在很多嵌入式产品中使用了它，它占用资源非常的低，在嵌入式设备中，可能只需要几百K的内存就够了。
1. Encapsulate the method of database operation;
module.exports = {
dbName:'gather',
dbPath:"_downloads/gather.db",
// 判断数据库是否打开
isOpen() {
// 数据库打开了就返回 true,否则返回 false
var open = plus.sqlite.isOpenDatabase({
name: this.dbName, // 数据库名称
path: this.dbPath // 数据库地址
})
return open;
},
// 创建数据库 或 有该数据库就打开
openSqlite() {
return new Promise((resolve, reject) => {
// 打开数据库
plus.sqlite.openDatabase({
name: this.dbName,
path: this.dbPath,
success(e) {
resolve(e); // 成功回调
},
fail(e) {
reject(e); // 失败回调
}
})
})
},
// 关闭数据库
closeSqlite() {
return new Promise((resolve, reject) => {
plus.sqlite.closeDatabase({
name: this.dbName,
success(e) {
resolve(e);
},
fail(e) {
reject(e);
}
})
})
},
// 数据库建表 sql:'CREATE TABLE IF NOT EXISTS dbTable("id" varchar(50),"name" TEXT)
// 创建 CREATE TABLE IF NOT EXISTS 、 dbTable 是表名，不能用数字开头、括号里是表格的表头
createTable(dbTable, data) {
return new Promise((resolve, reject) => {
// executeSql: 执行增删改等操作的SQL语句
plus.sqlite.executeSql({
name: this.dbName,
name: "gather",
sql: `CREATE TABLE IF NOT EXISTS ${
dbTable}(${
data})`,
success(e) {
resolve(e);
},
fail(e) {
reject(e);
}
})
})
},
// 数据库删表 sql:'DROP TABLE dbTable'
dropTable(dbTable) {
return new Promise((resolve, reject) => {
plus.sqlite.executeSql({
name: this.dbName,
sql: `DROP TABLE ${
dbTable}`,
success(e) {
resolve(e);
},
fail(e) {
reject(e);
}
})
})
},
// 向表格里添加数据 sql:'INSERT INTO dbTable VALUES('x','x','x')' 对应新增
// 或者 sql:'INSERT INTO dbTable ('x','x','x') VALUES('x','x','x')' 具体新增
// 插入 INSERT INTO 、 dbTable 是表名、根据表头列名插入列值
insertTableData(dbTable, data, condition) {
// 判断有没有传参
if (dbTable !== undefined && data !== undefined) {
// 判断传的参是否有值
var bol = (JSON.stringify(data) == "{}");
if (!bol) {
if (condition == undefined) {
var sql = `INSERT INTO ${
dbTable} VALUES('${
data}')`;
} else {
var sql = `INSERT INTO ${
dbTable} (${
condition}) VALUES(${
data})`;
}
return new Promise((resolve, reject) => {
// 表格添加数据
plus.sqlite.executeSql({
name: this.dbName,
sql: sql,
success(e) {
resolve(e);
},
fail(e) {
reject(e);
}
})
})
} else {
return new Promise((resolve, reject) => {
reject("错误添加") })
}
} else {
return new Promise((resolve, reject) => {
reject("错误添加") })
}
},
// 根据条件向表格里添加数据 有数据更新、无数据插入
// (建表时需要设置主键) 例如 --- "roomid" varchar(50) PRIMARY KEY
insertOrReplaceData(dbTable, data, condition) {
// 判断有没有传参
if (dbTable !== undefined && data !== undefined) {
if (condition == undefined) {
var sql = `INSERT OR REPLACE INTO ${
dbTable} VALUES('${
data}')`;
} else {
var sql = `INSERT OR REPLACE INTO ${
dbTable} (${
condition}) VALUES(${
data})`;
}
// console.log(sql);
return new Promise((resolve, reject) => {
// 表格添加数据
plus.sqlite.executeSql({
name: this.dbName,
sql: sql,
success(e) {
resolve(e);
},
fail(e) {
reject(e);
}
})
})
} else {
return new Promise((resolve, reject) => {
reject("错误添加") })
}
},
// 查询获取数据库里的数据 sql:'SELECT * FROM dbTable WHERE lname = 'lvalue''
// 查询 SELECT * FROM 、 dbTable 是表名、 WHERE 查找条件 lname,lvalue 是查询条件的列名和列值
// selectTableData(dbTable, uname, namevalue, upass, passvalue,urrn,rrnvalue) {
selectTableData(dbTable, uname,namevalue) {
if (dbTable !== undefined) {
// // 第一个是表单名称，后两个参数是列表名，用来检索
// if (uname !== undefined && upass !== undefined && urrn!==undefined) {
// // 三个检索条件
// var sql = `SELECT * FROM ${dbTable} WHERE ${uname} = '${namevalue}' AND ${upass} = '${passvalue}' AND ${urrn}='${rrnvalue}'`;
// }
// if (uname !== undefined && upass !== undefined &&urrn==undefined) {
// // 两个检索条件
// var sql = `SELECT * FROM ${dbTable} WHERE ${uname} = '${namevalue}' AND ${upass} = '${passvalue}'`;
// }
if (uname !== undefined ) {
// 一个检索条件
var sql = `SELECT * FROM ${
dbTable} WHERE ${
uname} = '${
namevalue}'`;
// console.log(sql);
}
if (uname == undefined) {
var sql = `SELECT * FROM ${
dbTable}`;
}
return new Promise((resolve, reject) => {
// 表格查询数据 执行查询的SQL语句
plus.sqlite.selectSql({
name: this.dbName,
sql: sql,
success(e) {
resolve(e);
},
fail(e) {
reject(e);
}
})
})
} else {
return new Promise((resolve, reject) => {
reject("错误查询") });
}
},
// 删除表里的数据 sql:'DELETE FROM dbTable WHERE lname = 'lvalue''
// 删除 DELETE FROM 、 dbTable 是表名、 WHERE 查找条件 lname,lvalue 是查询条件的列名和列值
// deleteTableData(dbTable, lname, lvalue, ww, ee) {
deleteTableData(dbTable, lname, lvalue) {
console.log("lname:" + lname + "," + "lvalue" + lvalue);
if (dbTable !== undefined) {
if (lname == undefined) {
var sql = `DELETE FROM ${
dbTable}`;
} else {
// if (ww !== undefined) {
// // 两个检索条件
// var sql = `DELETE FROM ${dbTable} WHERE ${lname} = '${lvalue}' AND ${ww} = '${ee}'`;
// } else {
// 一个检索条件
var sql = `DELETE FROM ${
dbTable} WHERE ${
lname} = '${
lvalue}'`;
// }
}
return new Promise((resolve, reject) => {
// 删除表数据
plus.sqlite.executeSql({
name: this.dbName,
sql: sql,
success(e) {
resolve(e);
},
fail(e) {
reject(e);
}
})
})
} else {
return new Promise((resolve, reject) => {
reject("错误删除") });
}
},
// 修改数据表里的数据 sql:"UPDATE dbTable SET 列名 = '列值',列名 = '列值' WHERE lname = 'lvalue'"
// 修改 UPDATE 、 dbTable 是表名, data: 要修改的列名=修改后列值, lname,lvalue 是查询条件的列名和列值
updateTableData(dbTable, data, lname, lvalue) {
if (lname == undefined) {
var sql = `UPDATE ${
dbTable} SET ${
data}`;
} else {
var sql = `UPDATE ${
dbTable} SET ${
data} WHERE ${
lname} = '${
lvalue}'`;
}
// WHERE 前面是要修改的列名、列值，后面是条件的列名、列值
return new Promise((resolve, reject) => {
// 修改表数据
plus.sqlite.executeSql({
name: this.dbName,
sql: sql,
success(e) {
resolve(e);
},
fail(e) {
reject(e);
}
})
})
},
// 获取指定数据条数 sql:"SELECT * FROM dbTable ORDER BY 'id' DESC LIMIT 15 OFFSET 'num'"
// dbTable 表名, ORDER BY 代表排序默认正序, id 是排序的条件 DESC 代表倒序，从最后一条数据开始拿
// LIMIT 15 OFFSET '${num}',这句的意思是跳过 num 条拿 15 条数据, num 为跳过多少条数据是动态值
// 例 初始num设为0，就从最后的数据开始拿15条，下次不拿刚获取的数据，所以可以让num为15，这样就能一步一步的拿完所有的数据
pullSQL(dbTable, id, num) {
return new Promise((resolve, reject) => {
plus.sqlite.selectSql({
name: this.dbName,
sql: `SELECT * FROM ${
dbTable} ORDER BY '${
id}' DESC LIMIT 15 OFFSET '${
num}'`,
success(e) {
resolve(e);
},
fail(e) {
reject(e);
}
})
})
}
}
2. Example of use: (provide the operation of creating a database table and adding data)
create a database table
createTable() {
let open = DB.isOpen();
if (open) {
let sql = '"id" INTEGER PRIMARY KEY AUTOINCREMENT,"monomerId" text,"monomerName" text,"code" text,"administrativeLocation" text,"longitude" real,"latitude" real,"newFind" text,"mainType" text,'
+ '"subtype" text,"basicType" text,"imageStr" text,"videoStr" text,"appearance" text,"intrinsicProperty" text,"composition" text,"geneticMechanism" text,"scaleAndVolume" text,'
+ '"envBackground" text,"relatedThings" text,"externalRoad" text,"ambitusCity" text,"ambitusCityDistance" text,"centreName" text,"centreDistance" text,"touristAreaName" text,"touristAreaDistance" text,'
+ '"otherInstructionsOne" text,"preservationStatus" text,"developed" text,"protective" text,"scenicSpotName" text,"scenicSpotGrade" text,"scenicAreaName" text,"scenicAreaGrade" text,"visitorReception" text,'
+ '"otherInstructionsTwo" text,"monomerScore" text,"maybeGrade" text,"filledBy" text,"contactNumber" text,"censusDate" text,"status" integer,"createTime" text,"createBy" text,"typeCode" text,"tourismResourcesJson" text,"directionlist" text';
// 创建表 DB.createTable(表名, 表的列)
DB.createTable("gatherTable", sql)
.then(res => {
console.log("创建gatherTable表成功");
})
.catch(error => {
console.log("创建表失败");
});
} else {
console.log("数据库未打开");
}
},
数据的插入
let open = DB.isOpen();
DB.insertTableData("gatherTable", sql, condition).then(res => {
uni.showToast({
title: "数据保存成功！",
position: 'center',
icon: 'none'
});
uni.navigateBack({
delta: 1
});
}).catch(error => {
console.log("失败", error);
});
The above is the effective operation method that I personally tested; friends who don’t understand are welcome to chat privately; if necessary, you can also like, comment and pay attention.