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How To Retrieve Primary Keys for SQL Server Tables


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Summary

When you create remote views using SQL Server tables as the data source, Visual FoxPro automatically sets the KeyField property to .T. for columns that are included in a primary index key. In some instances, you might want to retrieve the primary key information through code so you can get more detailed information about the key's structure. This article demonstrates how to use the stored procedure sp_pkeys to return primary key information from SQL Server.

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More information

The SQL Server stored procedure sp_pkeys returns information about columns explicitly defined with a PRIMARY KEY constraint. The sp_pkeys stored procedure is equivalent to SQLPrimaryKeys in ODBC. The results are ordered by TABLE_QUALIFIER, TABLE_OWNER, TABLE_NAME, and KEY_SEQ.
   Column Name     Data Type    Description
   ------------------------------------------------------------------------

   TABLE_QUALIFIER varchar(32)  The name of the table qualifier. This
                                column represents the database name, and it
                                might be NULL.
   TABLE_OWNER     varchar(32)  The name of the table owner. This column
                                represents the name of the database user
                                who created the table and it always returns
                                a value.
   TABLE_NAME      varchar(32)  The name of the table. This column
                                represents the table name as listed in the
                                sysobjects table, and it always returns a
                                value.
   COLUMN_NAME     varchar(32)  The name of the column, for each column
                                of the TABLE_NAME returned. This column
                                represents the column name as listed in the
                                syscolumns table, and it always returns a
                                value.
                                When a primary key involves multiple
                                columns, sp_pkeys returns one row for each
                                column used in the primary key expression.
   KEY_SEQ           smallint   The sequence number of the column in a
                                multi-column primary key, and it always
                                returns a value.
   PK_NAME         varchar(32)  A primary key identifier, and it is NULL if
                                it is not applicable to the data source.
				

Sample Code

Create a program named GETKeys.prg using the following code:

NoteYou must change UID=<username> and PWD=<strong password> to the correct values before you run this code. Make sure that UID has the appropriate permissions to perform this operation on the database.
   * Substitute the server name .
   #DEFINE Connect_String 'DRIVER={SQL Server};SERVER=MY_SERVER;' + ;
      'DATABASE=PUBS;UID=<user name>;PWD=<strong password>'
   * Create a cursor to store information.
   CREATE CURSOR SQLKeys (Table_Name C(128), Column_Name C(128), ;
      Key_Seq I, PK_Name C(128))
   * Connect to SQL Server.
   gnConnHandle=SQLSTRINGCONN(Connect_String)
   IF gnConnHandle>0
      * Get the tables available on SQL Server.
      SQLConnTables=SQLTABLES(gnConnHandle)
      IF SQLConnTables>0
         SELECT SQLResult
         INCnt=0
         DO WHILE !EOF()
            * Create a command to execute the stored procedure.
            SQLCommand="sp_pkeys " + ALLTRIM(Table_Name)
            * Execute the stored procedure and return data to a cursor.
            =SQLEXEC(gnConnHandle,SQLCommand,'syskeys')
            * Select the cursor.
            SELECT SYSKeys
            IF RECCOUNT()>0
               SCAN

                  IF RECNO()=1
                     * Insert a new record into the SQLKeys cursor.
                     INSERT INTO SQLKeys ;
                        VALUES ;
                        (SYSKeys.Table_Name, SYSKeys.Column_Name, ;
                        SYSKeys.Key_Seq,SYSKeys.PK_Name)
                  ELSE
                     * Multicolumn key.
                     * Concatenate to get the expression.
                     REPLACE SQLKeys.Column_Name WITH ;
                        ALLTRIM(SQLKeys.Column_Name) + ;
                        "+"  + ALLTRIM(SYSKeys.Column_Name)
                  ENDIF
               ENDSCAN
            ENDIF
            SELECT SQLResult
            SKIP
         ENDDO
         =SQLDISCONN(gnConnHandle)
      ENDIF
   ENDIF
   SELECT SQLKeys
   BROW LAST
   CLOSE ALL
   RETURN
					
Note that the Sales row column_name value is "stor_id+ord_num+title_id" and the TitleAuthor row column_name value is au_id+title_id.

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References

Transact - SQL Reference Help: sp_pkeys

(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by John Desch, Microsoft Corporation.

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Keywords: kbnosurvey, kbarchive, kbclientserver, kbdatabase, kbhowto, kbsqlprog, KB195526

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Article Info
Article ID : 195526
Revision : 6
Created on : 2/21/2014
Published on : 2/21/2014
Exists online : False
Views : 459