Alters the definition of a column, including the attributes of an existing identity column. Only the attributes specified will be altered. Others will remain unchanged.
The specified length, precision, and scale may be larger, smaller, or the same as the existing length, precision, and scale. However, if the new length, precision, or scale is smaller, truncation or numeric conversion errors may occur.
If the specified column has a default value and a new default value is not specified, the existing default value must represent a value that could be assigned to the column in accordance with the rules for assignment as described in Assignments and comparisons.
If the column is specified in a unique, primary, or foreign key, the new sum of the lengths of the columns of the keys must not exceed 32766-n, where n is the number of columns specified that allow nulls.
Changing the attributes will cause any existing values in the column to be converted to the new column attributes according to the rules for assignment to a column, except that string values will be truncated.
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