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WHERE Primary Key Column = Some Value UPDATE My Table SET Column1 = Some Other Table. I've seen developers use these approaches to duplicate data across multiple tables so that it's "easier" or "quicker" to write a query to read the data, but such actions are (usually) folly.
Only the partitions (or subpartitions) listed are checked for matches, and a row that is not in any of these partitions or subpartitions is not updated, whether it satisfies the clause, are flagged as unsafe for statement-based replication.
Table Structures and values: Table A has four columns: a, b, c, d (a is the primary key column) Table B has five columns: a1, b1, c1, d1, e1 (a1 and b1 together constitute the primary key for this table) The foreign key relationship between the two tables is based on A.a = B.a1 The data in these 2 tables is as follows: I. Table B a1 b1 c1 d1 e1 1 x1 y1 z1 40 2 a1 b1 c1 50 The requirement is to write a SQL to update columns b, c and d in Table A from the columns b1, c1 and d1 from Table B where-ever the join condition satisfies and e1 40) / Results after the update: a b c d ———————————— 1 x y z 2 a1 b1 c1 3 t x z SQL Server: UPDATE TABLEA SET b = TABLEB.b1, c = TABLEB.c1, d = TABLEB.d1 FROM TABLEA, TABLEB WHERE TABLEA.a = TABLEB.a1 AND TABLEB.e1 40 GO Note: This is an extension in SQL Server i.e.
the FROM clause – it does make it simple to understand and is a nice feature.
The reason I am mentioning this is because I have seen people write wrong where clauses and then wondering what went wrong because they specified the correct condition in the SET clause.
works fine when I try to update all the records in tbl A, however, in this case I only have missing data which I have identified and populated in tbl B.