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AskSQLTeam
Ask SQLTeam Question
0 Posts |
 Posted - 2002-01-27 : 20:53:17
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| Jain writes "I have the following relational schema:Table_A(time_stamp,A_var,prim_key_B)Table_B(prim_key_B,B_name)Table_C(prim_key_B,C_var1,C_var2)Table_D(prim_key_B,D_var1,D_var2)time_stamp is primary key for Table_Aprim_key_B is primary key for Table_B,C,DTable_B is superclass with Table_C and Table_D as its subclasses.prim_key_B, which is an autogenerated key, links Table_A with Table_B.B_name has values(CHAR) which are exactly same as the name of Table_C and Table_D.My requirement is following:I want to display all the attributes of Table_A, B_name, and all the attributes of the related subclass.I am facing problem in locating the right subclass although from B_name I know the name of the subclass to refer.Could you please send me the SQL query for the above requirement.Thanks in advance!" |
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Nazim
A custom title
1408 Posts |
Posted - 2002-01-28 : 00:48:39
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IMHO, You have a poorly designed database.when you have stated that prim_key_B links the table , why should you locate for B_name?.quote:
Table_B is superclass with Table_C and Table_D as its subclasses.prim_key_B, which is an autogenerated key, links Table_A with Table_B.B_name has values(CHAR) which are exactly same as the name of Table_C and Table_D.I am facing problem in locating the right subclass although from B_name I know the name of the subclass to refer
Anywayz , Hope this query does what you are looking forselect b.Prim_key_B,a.time_stamp,a.b_name,c.C_var1,c.C_var2,D.D_Var1,D._var2from Time_B a left joinTime_A bon a.prim_key_b=b.prim_key_bleft join time_C con a.prim_key_b=c.prim_key_b --or b_name with either c_var1 or c_var2left join time_d don on a.prim_key_b=d.prim_key_b --or b_name with either d_var1 or d_var2Post your requirements with your other table schema's . we will try to assist you in your design changes.--------------------------------------------------------------Dont Tell God how big your Problem is , Tell the Problem how Big your God isEdited by - Nazim on 01/28/2002 00:50:32 |
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Problem in accessing subclasses