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Updating one table from another table in sql server 2016

For more information, see CAST and CONVERT (Transact-SQL).Reducing the precision or scale of a column may cause data truncation.

To generate unique values for each column, either use the NEWID function on INSERT statements or specify the NEWID function as the default for the column.For a list and more information, see Windows Collation Name (Transact-SQL) and SQL Server Collation Name (Transact-SQL).The COLLATE clause can be used to change the collations only of columns of the char, varchar, nchar, and nvarchar data types.To change the collation of a user-defined alias data type column, you must execute separate ALTER TABLE statements to change the column to a SQL Server system data type and change its collation, and then change the column back to an alias data type.ALTER COLUMN cannot have a collation change if one or more of the following conditions exist: NULL | NOT NULL Specifies whether the column can accept null values.If the new column does not allow null values and the table is not empty, a DEFAULT definition must be added with the new column, and the new column automatically loads with the default value in the new columns in each existing row.

NULL can be specified in ALTER COLUMN to force a NOT NULL column to allow null values, except for columns in PRIMARY KEY constraints.

If the table is not in the current database or is not contained by the schema owned by the current user, the database and schema must be explicitly specified.

ALTER COLUMN Specifies that the named column is to be changed or altered.

If not specified, the column is assigned the default collation of the database.

Collation name can be either a Windows collation name or a SQL collation name.

NOT NULL can be specified in ALTER COLUMN only if the column contains no null values.