In this system development, there is a case where data interaction with other system is encountered, including data download and data backup. (The latter does not introduce this article). Download, that is, the system needs to download basic business data from other systems database, and after the data source is updated, the business base data of the system also needs to update (no real-time), and the data source has several basic business data of nearly 100. Wan Wan. In order to facilitate the description, only one table is discussed, the data source table is a table, downloaded to the system's expression as B table ideas: Download data from A table to B table processing can be divided into 2 steps: 1 The first download first download should be to insert all the data corresponding to the A table to the B table (complete time when the system is initialized) This process is better, and a SQL can get it. 2. Second (and later) Downloadings 2 cases: a Table Add data and original data updates. In order to determine which data needs to be processed, the determination can be determined according to the last update time recorded in the A table (as the system of the data source, the last update time field, the following is LaStupdateTime) is determined: ie, if the value of the LastupdateTime recorded in the table LaStupDateTime value greater than B table data is considered to be processed data: a. When such records do not exist in this system, it is new business data B. When such records are present, they need to update data for this system. If the value of the LastupDateTime is not greater than the value of the value of the B table data is not required to be processed. Therefore, in this case download data can be divided into 2 steps: The first step is to download the new record to the second step of this system. Second steps to update the data that needs to be updated, whether it is data insert or data update, In this system, it is necessary to record or update its LaseDateDate, otherwise it will not be able to compare the LastUpdateTime in the table in the table later and the LastUpdateTime in the table. When the amount of data is large, it will be time consuming for a certain time. To this end, a table C can be built separately and use a record to save the final update time of the B table, which is updated as long as the table C is updated, and only one record is updated, and the performance improvement can be obtained. According to the above analysis, we have taken the following scenario: 1. Table 2. Table 2. of the basic data table structure in this system is similar (taken only required data), establish a table C, specifically used to record each system Business Data Sheet Last Update Record Date, the table structure is as follows: CREATE TABLE C (TableName, VARCHAR (50), Lastupdatedate Date) 3. When completing the data inserted or updated data, the corresponding record according to the data according to the processing per time. LastupDateTime needs to be aware of: 1. When updating LastUpDateTime, when the table is updated, its time does not use the time of the system, but should take the time of the system where the data source is located. 2. When the base form is small (less business data), the data in the destination table can be deleted each time the download is executed and downloaded, the method used in this article is not required.
