Is there any difference between COUNT('') and COUNT(*) and COUNT(1) and COUNT(ColumnName)? What approach is faster?
Is there any difference between COUNT(”) and COUNT(*) and COUNT(1) and COUNT(ColumnName) ? What
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Is there any difference between COUNT('') and COUNT(*) and COUNT(1) and COUNT(ColumnName)? What approach is faster?
Count(ColumnName)is influenced by the value of the column. The other variants do effectively the same.Count(*)is slower in some databases (MySQL amongst others), because it retrieves all fields while it doesn’t have to. That’s whay often'x'or1is used to be safe. SQL Server and Oracle are somewhat smarter and don’t retrieve field values if they don’t have to.Note that
''equalsNULLon Oracle (yes it does!), which may have an undesired effect there. Not a problem for SQL Server, but you can use1to be safe.