--新建表/CREATETABLE列级完整性约束条件列级完整型约束条件.../createtableStudentSnochar9primarykey/Sno是主码/Snamechar20unique/Sname取唯一值/Ssexchar2SagesmallintSdeptchar20--修改表/ALTERTABLEADD完整性约束ALTERCOLUMNDROP/altertableStudentaddS_entrancevarchar20altertableStudentdropS_entrance--删除表/DROPTABLERISTRICTCASCADE/--若选择RISTRICT：则该表的删除使有限制的，欲删除的表不能被其他表的约束所引用。如果存在依赖该表的对象，则此表不能被删除。--若选择CASCADE：则该表的删除没有限制，删除该基本表是，相关依赖对象，例如视图，都将被一起删除。droptableStudent--插入数据//insertintoStudentSnoSnameSsexSageSdeptvalues200215121李勇男20CSinsertintoStudentSnoSnameSsexSageSdeptvalues200215122刘晨女19CSinsertintoStudentSnoSnameSsexSageSdeptvalues200215123王敏女18MAinsertintoStudentSnoSnameSsexSageSdeptvalues200215125张立男19IScreatetableCourseCnochar4primarykeyCnamechar40Cpnochar4/Cpno的含义是先修课/CcreditsmallintforeignkeyCpnoreferencesCourseCno/表级完整性约束条件，Cpno是外码，被参照列是Cno//外键引用列的值必须存在且唯一/droptableCourseselectfromCourse/插入的数据先行课必须存在才能插入/insertintoCourseCnoCnameCpnoCcreditvalues2数学null2insertintoCourseCnoCnameCpnoCcreditvalues6数据处理null2insertintoCourseCnoCnameCpnoCcreditvalues4操作系统63insertintoCourseCnoCnameCpnoCcreditvalues7PASCAL语言64insertintoCourseCnoCnameCpnoCcreditvalues5数据结构74insertintoCourseCnoCnameCpnoCcreditvalues1数据库54insertintoCourseCnoCnameCpnoCcreditvalues3信息系统14createtableSCSnochar9Cnochar4GradesmallintprimarykeySnoCno/主码由两个属性构成，必须作为表级完整性进行定义/foreignkeySnoreferencesStudentSno/表级完整性约束条件，Sno是外码，被参照表是Student/foreignkeyCnoreferencesCourseCno/表级完整性约束条件，Cno是外码，被参照表是Course/droptableSCselectfromSCinsertintoSCSnoCnoGradevalues200215121192insertintoSCSnoCnoGradevalues200215121285insertintoSCSnoCnoGradevalues200215121388insertintoSCSnoCnoGradevalues200215121489insertintoSCSnoCnoGradevalues200215121578insertintoSCSnoCnoGradevalues200215121677insertintoSCSnoCnoGradevalues200215121777insertintoSCSnoCnoGradevalues200215122290insertintoSCSnoCnoGradevalues200215122380selectfromStudentselectfromCourseselectfromSC--插入数据--INSERTINTO...VALUES.../INSERTINTO...子查询/createtableDept_ageSdeptchar15Avg_agesmallintINSERTINTODept_ageSdeptAvg_ageSELECTSdeptAVG