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<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2//EN"><HTML><HEAD> <TITLE>Teach Yourself SQL in 21 Days, Second Edition -- Week 2 In Review</TITLE></HEAD><BODY TEXT="#000000" BGCOLOR="#FFFFFF"><CENTER><H1><IMG SRC="../buttonart/sams.gif" WIDTH="171" HEIGHT="66" ALIGN="BOTTOM" BORDER="0"><BR><FONT COLOR="#000077">Teach Yourself SQL in 21 Days, Second Edition</FONT></H1></CENTER><CENTER><P><A HREF="../ch14/ch14.htm"><IMG SRC="../buttonart/previous.gif" WIDTH="128" HEIGHT="28"ALIGN="BOTTOM" ALT="Previous chapter" BORDER="0"></A><A HREF="../wk3ag/wk3ag.htm"><IMGSRC="../buttonart/next.gif" WIDTH="128" HEIGHT="28" ALIGN="BOTTOM" ALT="Next chapter"BORDER="0"></A><A HREF="../index.htm"><IMG SRC="../buttonart/contents.gif" WIDTH="128"HEIGHT="28" ALIGN="BOTTOM" ALT="Contents" BORDER="0"></A> <HR></CENTER><CENTER><H1><FONT COLOR="#000077">Week 2 In Review</FONT></H1></CENTER><P>Week 1 spent a great deal of time introducing a very important topic: the <TT>SELECT</TT>statement. Week 2 branched out into various topics that collectively form a thoroughintroduction to the Structured Query Language (SQL).</P><P>Day 8 introduced data manipulation language (DML) statements, which are SQL statementsthat you can use to modify the data within a database. The three commands most commonlyused are <TT>INSERT</TT>, <TT>DELETE</TT>, and <TT>UPDATE</TT>. Day 9 described howto design and build a database and introduced the commands <TT>CREATE DATABASE</TT>and <TT>CREATE TABLE</TT>. A table can be created with any number of fields, eachof which can be a database-vendor-defined data type. The <TT>ALTER DATABASE</TT>command can change the physical size or location of a database. The <TT>DROP DATABASE</TT>and <TT>DROP TABLE</TT> statements, respectively, remove a database or remove a tablewithin a database.</P><P>Day 10 explained two ways to display data: the view and the index. A view is avirtual table created from the output of a <TT>SELECT</TT> statement. An index ordersthe records within a table based on the contents of a field or fields.</P><P>Day 11 covered transaction management, which was your first taste of programmingwith SQL. Transactions start with the <TT>BEGIN TRANSACTION</TT> statement. The <TT>COMMITTRANSACTION</TT> saves the work of a transaction. The <TT>ROLLBACK TRANSACTION</TT>command cancels the work of a transaction.</P><P>Day 12 focused on database security. Although the implementation of database securityvaries widely among database products, most implementations use the <TT>GRANT</TT>and <TT>REVOKE</TT> commands. The <TT>GRANT</TT> command grants permissions to auser. The <TT>REVOKE</TT> command removes these permissions.</P><P>Day 13 focused on developing application programs using SQL. Static SQL typicallyinvolves the use of a precompiler and is static at runtime. Dynamic SQL is very flexibleand has become very popular in the last few years. Sample programs used Dynamic SQLwith the Visual C++ and Delphi development toolkits.</P><P>Day 14 covered advanced aspects of SQL. Cursors can scroll through a set of records.Stored procedures are database objects that execute several SQL statements in a row.Stored procedures can accept and return values. Triggers are a special type of storedprocedure that are executed when records are inserted, updated, or deleted withina table.</P><H1></H1><CENTER><P><HR><A HREF="../ch14/ch14.htm"><IMG SRC="../buttonart/previous.gif" WIDTH="128" HEIGHT="28"ALIGN="BOTTOM" ALT="Previous chapter" BORDER="0"></A><A HREF="../wk3ag/wk3ag.htm"><IMGSRC="../buttonart/next.gif" WIDTH="128" HEIGHT="28" ALIGN="BOTTOM" ALT="Next chapter"BORDER="0"></A><A HREF="../index.htm"><IMG SRC="../buttonart/contents.gif" WIDTH="128"HEIGHT="28" ALIGN="BOTTOM" ALT="Contents" BORDER="0"></A><BR><BR><BR><IMG SRC="../buttonart/corp.gif" WIDTH="284" HEIGHT="45" ALIGN="BOTTOM" ALT="Macmillan Computer Publishing USA"BORDER="0"></P><P>© <A HREF="../copy.htm">Copyright</A>, Macmillan Computer Publishing. Allrights reserved.</CENTER></BODY></HTML>⌨️ 快捷键说明
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