============================================
sql : union union all difference
============================================
The Short Answer: SQL UNION vs. UNION ALL. The key difference is that UNION removes duplicate records, whereas UNION ALL includes all duplicates.
This distinction not only changes the number of rows in the query result, but it also impacts performance
so always use UNION ALL instead of UNION to speed up the execution time
============================================
DIFFERENCE between joins and union
joins combine data side-by-side, whereas unions combine data one on top of the other
------------------------------------------------------------------------------------------------------
VARCHAR AND NVARCHAR difference
In database contexts, VARCHAR and NVARCHAR are data types used to store variable-length text strings.
The key difference lies in their encoding:
VARCHAR uses single-byte character sets (like ASCII),
while NVARCHAR
uses Unicode, allowing for a wider range of characters including those from multiple languages. NVARCHAR typically requires more storage space and has a shorter maximum character length compared to VARCHAR
------------------------------------------------------------------------------------------------------
No comments:
Post a Comment