基础3sql server数据库5 Sql语句简单理解就是用于操作的

Dns解析系Ip地址\MysqlSqlSQLSql o’’World!’ 数据库对象(表名,库中名,列名可以用[]括起来,1)防止和关键字2)对象名之间有空DroptableDropdatabase要删除的数据库名修改表语法:altertable表名……修改表结构时,一定要注意会不会原来表中的数据有--altertable表名dropcolumn要删除的列名;altertabletblStudentdropcolumntSCla --altertable表名addaltertabletblStudentadd --altertable表名altercolumnaltertabletblStudentaltercolumn intnot--altertable表名addconstraint主键约束名primarykey(主键列)altertableTblStudentaddconstraintPK_TblStudent_tSIdPrimaryaltertabletblStudentdropconstraint对数据库,最常用的就是增 删 改 查查:语法 Select*from表 显示表中的所有数useselect*fromStudent--select后的*,SELECTstuId,stuAddress,'我也不知道asnewColfromselectstuName,stuAddress,stuName+stuAddressas'+地址'fromselecttestId+stuIdfromSELECTstuIdas学号],stuName,stuAddressfromSELECTstuIdas[学号],stuName,stuAddressfromSELECTstuIdas[学号],stuName,'地址'=stuAddressfrom--要求：两个结果集的列数必须相同2两个结果集对应列的数据类型相同select*fromScoreselectstuId,testBasetestName,testDatefromscorewherestuId=1union--合并结果集selectstuId,testBase,testName,testDatefromscorewhereselectcol1from selectCol2as'aaa'fromtblTest2--语法:insertinto表名(列名，列名 insertintoTblClass(tClassName,tClassDesc)insertintoTblClass(tClassName) select*from--insertintoTblClass(tClassDescvalues('这里是描述insertintoTblClassvalues('未命名班','还没想好班名--SETIDENTITY_INSERT表名setidentity_inserttblclassinsertintoTblClass(tCla setidentity_inserttblclassOff不允许手动设置自动增涨列了insertintoTblClass(tClassName,tClassDesc)select*fromTblClass--语法：insertinto表名[(列名,列 insertintoTblClass(tClassName,tClassDesc)select'','我喜欢的地方'unionselect'班','明天开unionselect'','都是'unionselect'杨','班'insertintoselecttSAddress,tSPhonefromTblStudentselect*fromTblClassinsertintoselecttSGender,tSAddress,tSPhone,tSAge,tSBirthday,tSCardId,tSCla fromTblStudentselect*fromTblStudent--select*from表名在列名后加上into新表名注意：新表必须不存在select*intonewClassAfromTblClassselecttClassName,tClassDescintonewClassColsfromTblClassselect*fromnewClasscolsselect*fromselecttClassName,tClassDescintonewClassWherefromTblClasswheretCla select*fromupdate表名set要更新的列名=新值[,要更新的列名=新值[where表达式]useTestDataBaseselect*intonewStudentfromStudentselect*fromnewStudentupdatenewStudentset updatenewStudentsetstuIsDel=1,cla select*fromnewStudentupdaTEnewStudentset select*fromupdateScoresettestBase=testBase-1select*fromscoreselect*fromScorewhereupdateScoresettestBase=testBase+5wherestuId=1select*fromScorewherestuId=1delete--删除的语法deletefrom表名select*fromnewStudentdeletefromnewStudentselect*fromselect*fromnewStudentwherecla =1andstu deletefromnewStudentwherecla =1andstu --语法truncatetableselect*fromnewStudenttruncatetable约束是保证数据库完数据为完整性说白了就是保证数据库中的比如:,只有男和女 唯一约束:select*frominsertintoTblClassvalues('期','12-28')deletefromTblClasswheretCla --语法altertable表名addconstraint约束名约束的关键字(列名)...altertabletblclassaddconstraintUQ_tblClass_tClassDescUnique(tClassDesc)select*fromTblClassinsertintoTblClass(tClassDesc)values('ttt12-28altertabletblClassaddconstraintDF_TblClass_tClassDescDefault(N'')fortClassDescinsertintoTblClass(tClassName)values('测试就业班')updateTblClasssettclassmaxstudent=50select*fromTblClassinsertintoTblClassvalues('11',' selectLEN(tclassName),tclassNamefromTblClassaltertabletblClassaddconstraintCK_