add upgrade opt

Signed-off-by: Nleiiyb <leiyanbo@huawei.com>

zh-cn/application-dev/database/data-persistence-by-rdb-store.md

@@ -65,9 +65,9 @@
          securityLevel: relationalStore.SecurityLevel.S1 // 数据库安全级别
        };
 
+       // 假设当前数据库版本为3，表结构：EMPLOYEE (NAME, AGE, SALARY, CODES)
        const SQL_CREATE_TABLE = 'CREATE TABLE IF NOT EXISTS EMPLOYEE (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT NOT NULL, AGE INTEGER, SALARY REAL, CODES BLOB)'; // 建表Sql语句
 
-       // 假设当前数据库版本为3
        relationalStore.getRdbStore(this.context, STORE_CONFIG, (err, store) => {
          if (err) {
            console.error(`Failed to get RdbStore. Code:${err.code}, message:${err.message}`);
@@ -75,7 +75,6 @@
          }
          console.info(`Succeeded in getting RdbStore.`);
 
-        // 这里执行升降级操作
         // 当数据库创建时，数据库默认版本为0
         if (store.version == 0) {
           store.executeSql(SQL_CREATE_TABLE); // 创建数据表
@@ -83,17 +82,18 @@
           store.version = 3;
         }
 
+        // 如果数据库版本不为0且和当前数据库版本不匹配，需要进行升降级操作
         // 当数据库存在并假定版本为1时，例应用从某一版本升级到当前版本，数据库需要从1版本升级到2版本
         if (store.version != 3 && store.version == 1) {
-          // version = 1：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES) => version = 2：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES, ADDRESS)
-          store.executeSql("ALTER TABLE EMPLOYEE ADD COLUMN ADDRESS TEXT", null);
+          // version = 1：表结构：EMPLOYEE (NAME, SALARY, CODES, ADDRESS) => version = 2：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES, ADDRESS)
+          store.executeSql("ALTER TABLE EMPLOYEE ADD COLUMN AGE INTEGER", null);
           store.version = 2;
         }
 
         // 当数据库存在并假定版本为2时，例应用从某一版本升级到当前版本，数据库需要从2版本升级到3版本
         if (store.version != 3 && store.version == 2) {
-          // version = 2：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES, ADDRESS) => version = 3：表结构：EMPLOYEE (NAME, SALARY, CODES, ADDRESS)
-          store.executeSql("ALTER TABLE EMPLOYEE DROP COLUMN AGE INTEGER", null);
+          // version = 2：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES, ADDRESS) => version = 3：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES)
+          store.executeSql("ALTER TABLE EMPLOYEE DROP COLUMN ADDRESS TEXT", null);
           store.version = 3;
         }
 
@@ -118,10 +118,10 @@
      name: 'RdbTest.db', // 数据库文件名
      securityLevel: relationalStore.SecurityLevel.S1 // 数据库安全级别
    };
-   
+
+   // 假设当前数据库版本为3，表结构：EMPLOYEE (NAME, AGE, SALARY, CODES)
    const SQL_CREATE_TABLE = 'CREATE TABLE IF NOT EXISTS EMPLOYEE (ID INTEGER PRIMARY KEY AUTOINCREMENT, NAME TEXT NOT NULL, AGE INTEGER, SALARY REAL, CODES BLOB)'; // 建表Sql语句
 
-   // 假设当前数据库版本为3
    relationalStore.getRdbStore(context, STORE_CONFIG, (err, store) => {
      if (err) {
        console.error(`Failed to get RdbStore. Code:${err.code}, message:${err.message}`);
@@ -129,7 +129,6 @@
      }
      console.info(`Succeeded in getting RdbStore.`);
 
-     // 这里执行升降级操作
      // 当数据库创建时，数据库默认版本为0
      if (store.version == 0) {
         store.executeSql(SQL_CREATE_TABLE); // 创建数据表
@@ -137,17 +136,18 @@
         store.version = 3;
      }
 
+     // 如果数据库版本不为0且和当前数据库版本不匹配，需要进行升降级操作
      // 当数据库存在并假定版本为1时，例应用从某一版本升级到当前版本，数据库需要从1版本升级到2版本
      if (store.version != 3 && store.version == 1) {
-        // version = 1：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES) => version = 2：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES, ADDRESS)
-        store.executeSql("ALTER TABLE EMPLOYEE ADD COLUMN ADDRESS TEXT", null);
+        // version = 1：表结构：EMPLOYEE (NAME, SALARY, CODES, ADDRESS) => version = 2：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES, ADDRESS)
+        store.executeSql("ALTER TABLE EMPLOYEE ADD COLUMN AGE INTEGER", null);
         store.version = 2;
      }
 
      // 当数据库存在并假定版本为2时，例应用从某一版本升级到当前版本，数据库需要从2版本升级到3版本
      if (store.version != 3 && store.version == 2) {
-        // version = 2：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES, ADDRESS) => version = 3：表结构：EMPLOYEE (NAME, SALARY, CODES, ADDRESS)
-        store.executeSql("ALTER TABLE EMPLOYEE DROP COLUMN AGE INTEGER", null);
+        // version = 2：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES, ADDRESS) => version = 3：表结构：EMPLOYEE (NAME, AGE, SALARY, CODES)
+        store.executeSql("ALTER TABLE EMPLOYEE DROP COLUMN ADDRESS TEXT", null);
         store.version = 3;
      }