javascript - sqlite 检查提供的数据是否存在，则警报存在，否则警报不存在

Question

我正在尝试检查选择查询中提供的数据是否存在，然后提醒数据存在，否则提醒数据不存在，但我不知道如何实现这一点。

Demo Fiddle

var db = openDatabase("demo", "1.0", "demo", 200000);

            db.transaction(function(tx) {
            tx.executeSql( "CREATE TABLE IF NOT EXISTS test (Slno INTEGER PRIMARY KEY AUTOINCREMENT, column1 TEXT UNIQUE, column2 TEXT UNIQUE, column3 TEXT UNIQUE, column4 TEXT UNIQUE, column5 TEXT UNIQUE)");
        },errorHandler);

db.transaction(function(tx) {
            tx.executeSql("INSERT INTO test (column1, column2 ,column3, column4,column5) VALUES ('insert1','insert2','insert3','insert4','insert5');");
        },errorHandler);

选择查询

db.transaction(function(tx) {
            tx.executeSql("SELECT * FROM test where column1='insert1'");
        },errorHandler,successHandler);


function errorHandler(error) {
    alert("Error : " + error.message);
}

function successHandler  (transaction, resultSet) {
            alert(resultSet.length);
}

Answer 1

您收到:-

Error : could not execute statement due to a constaint failure (19 UNIQUE constraint failed: test.column5)

因为浏览器会记住之前的插入，并且列是唯一的。

并且您的所选交易存在轻微的格式问题，请尝试将其更改为:-

db.transaction(function(tx) {
    tx.executeSql("SELECT * FROM test where column1='insert1'", [], successHandler, errorHandler);
},errorHandler);

完整答案:-

var db = openDatabase("demo", "1.0", "demo", 200000);

db.transaction(function(tx) {
    tx.executeSql( "CREATE TABLE IF NOT EXISTS test (Slno INTEGER PRIMARY KEY AUTOINCREMENT, column1 TEXT UNIQUE, column2 TEXT UNIQUE, column3 TEXT UNIQUE, column4 TEXT UNIQUE, column5 TEXT UNIQUE)");
},errorHandler);

db.transaction(function(tx) {
    tx.executeSql("SELECT * FROM test where column1='insert1'", [], successHandler, errorHandler);
},errorHandler);

function errorHandler(error) {
    alert("Error : " + error.message);
}

function successHandler  (transaction, resultSet) {
    alert(resultSet.rows.length);
}

Fiddle