With row-level compression, an index compresses each record at the row level. When row-level compression is enabled, a number of changes are made to each record. The metadata for the row is stored in an alternative format that decreases the amount of information stored on each column, but because of another change it may actually increase the size of the overhead. The main changes to the records are numerical data
changes from fixed to variable length and blank spaces at the end of fixed-length string data types that are not stored. Another change is that null or zero values do not require any space to be stored.
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