This means that you have to select on all the fields which comprise a unique key -- a non-unique primary key is not sufficient.
Without uniqueness, you are reduced to something like @Paul Karr's loop -- and if there is not a unique correlation, then more than one target row may be updated for each source row.
When I try to update only the missing data the non-matched data is also updated but to NULL. The reason some of your rows are getting NULLs updated is due to the subquery.
When the subquery fails to find a matching row in tbl B, the subquery returns NULL.
If this happens, the UPDATE will terminate with an error ("subquery may return only one row").
I have one table A has column (id, field_1,field_2), and another table B has column (id,field_2) Now I want to merge table B to A, that means i want to update field_2 in table A to value of table B. BTW I am using oracle Thanks Now, each time the above is executed, it will do it across all rows in the table.
Additionally -- given the way the where and set clauses are CODED in the above -- it would succeed. The Headoffice is merge the data into their system. For migration data first of all i create another temporary user named VISTEMP then cotinuing this kinds of code insert into VISTEMP. Now we can update the join: update ( select a.pop, from taba a, gtt b where = ) set pop = cnt / and thats it. Hi Tom, Im selecting approximately 1 million records from some tables and populating another set of tables.
The query would in fact execute without any error messages since the correlated subquery in SET clause returns EXACTLY one row for each row in B and the where clause executes without error. Lets say you have a table A ( id int, a1 varchar2(25) ) and a table B ( id int PRIMARY KEY, b1 varchar2(25) ). REGISTRATION(BIN, NAME, NAME_ALIAS, COR_GROUP, AUTHOBY, AUTHODATE, CG_NAME, ADD1, ADD2, ADD3, TEL1, FAX1, ADD5, ADD6, ADD7, TEL2, FAX2, ADD9, ADD10, ADD11, TEL3, FAX3, TP_TYPE, TRD_LINC, TRD_FY, TRD_AUTH, IMP_REG, EXP_REG, REG_TYPE, TIN, STATUS, PRE_BIN, DATREG, STAT_CHNG, ACT_CODE, ACT_MULT, ITEM_TYPE, OLD_ACT, APP_CAT, LCODE, ISSUE_DATE, VREG, M_POSI, MFUNC, SFUNC, LAST_USER, LAST_ACCS, TREG, PAY_FREQ, CREG, EREG, OREG, OP_BAL, OP_BAL_DT) select BIN, NAME---- from VIS. Thank u very much for ur kind & very helpful reply. Here the source tables have data with leading spaces and the target data should be without spaces.
You may wish to update records in one table based on values in another table.
Since you can't list more than one table in the Oracle UPDATE statement, you can use the Oracle EXISTS clause.
The update query below shows that the PICTURE column is updated by looking up the same ID value in CATEGORY_ID column in table Categories_Test and Categories. If you need to update multiple columns simultaneously, use comma to separate each column after the SET keyword. Here we only want to update PICTURE column in Categories_Test table where the data in Category_Name column is Seafood in table Categories. Software and hardware names mentioned on this site are registered trademarks of their respective companies.