Sql updating primary key value
If a table has a primary key defined on any field(s), then you cannot have two records having the same value of that field(s).Note − You would use these concepts while creating database tables.Some of the common ones are: In these cases, the UPDATE statement execution stops and the UPDATE generates an error.No rows from the UPDATE statement are saved into the table, even those rows that didn’t generate an error.If you want to keep all rows from both select statement’s results use the ALL keyword Both joins and unions can be used to combine data from one or more tables into a single results. Whereas a join is used to combine columns from different tables, the union is used to combine rows.
A use case may be that you have two tables: Teachers and Students.This “all or nothing” behavior can be modified for arithmetic errors. An exclusive (X) lock is always placed on a table when an update is run.The lock is held in place until the update statement completes.When SET ANSI_PADDING OFF then CHAR data types are padded with spaces, VARCHAR data types have trailing spaces removed, and VARBINARY have trailing zeros removed.
For instance, if a field is defined as CHAR(10) and you update the value ‘Kris’ into this column, then it will be padded with six spaces.The UPDATE statement is complex and there are many elements to consider. For a full list check out the UPDATE (Transact-SQL) article.