Lesson-3培训课件.pptVIP

Committing an updated value After previous call to updateXXX, database is still not updated, only ResultSet is. Must call updateRow() to complete operation with dbms. call cancelRowUpdates() to cancel an update that you no longer wish to commit Note that all row references refer to ResultSet object, which may differ from database table modulo updates! 精品文档 Inserting rows Also can insert values directly in Java. Must move cursor to special row called insert row and then call insert method. uprs.moveToInsertRow(); uprs.updateString(COF_NAME, Kona); uprs.updateInt(SUP_ID, 150); uprs.updateFloat(PRICE, 10.99); uprs.updateInt(SALES, 0); uprs.updateInt(TOTAL, 0); uprs.insertRow(); updates both dbase and ResultSet at same time 精品文档 SQL Used to stand for “Structured Query Language”. Standard language for conversing with relational databases. Composed of three sub-languages: Data Definition Language (DDL) Data Control Language (DCL) Data Manipulation Language (DML) 精品文档 DDL Lets you define and revise the structure of relational databases. Examples: Create Database name [options] Create Table name ( columname datatype, … ) Only simple datatypes supported. 精品文档 DCL Lets user specify data security and integrity mechanisms that safeguard data Not very standardized – varies from vendor to vendor. 精品文档 DML Functionality for retrieving, manipulating, deleting, sorting, searching data. Examples just to get flavor: Select * From table; Select columns From tables [Where condition]; Select ItemNo, Qty From InvoiceLine; Insert Into InvoiceLine; (InvoiceNo, LineNo, CustomerNo) Values (101, 100, 10); 精品文档 How to use SQL Database vendor typically supplies GUI front-end for issuing SQL queries. Also usually supplies a scripting front-end for issuing SQL commands. Called Interactive SQL, good for developing and debugging queries Of limited use because cannot share data with program variables. From within a programming language Embedded SQL 精品文档 JDBC Ja