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How many columns in a table affect query performance?
CASE 1: I have a table with 30 columns and I query using 4 columns in the where clause. CASE 2: I have a table with 6 columns and I query using 4 columns in the where clause. What is the difference in performance in both cases?
Why are there fewer columns in a select?
The mainbenefit of returning fewer columns in a SELECTis that SQL might be able to avoid reading from the table / cluster, and instead, if it can retrieve all the selecteddata from an index(either as indexed columns and / or included columns in the case of a covering index).
Why are index suggestions not making execution faster?
Index suggestions are made by the query optimizer. If it comes across a logical selection from a table which is not well served by an existing index, it may add a “missing index” suggestion to its output. These suggestions are opportunistic; they are not based on a full analysis of the query, and do not take account of wider considerations.
Which is query slows down due to the index?
Now the query which slows down due to the index (the query is meaningless since it is created for testing only): With clustered index enabled: (1 row (s) affected) Table ‘IndexTestTable’. Scan count 4, logical reads 60, physical reads 0, read-ahead reads 0, lob logical reads 0, lob physical reads 0, lob read-ahead reads 0.
Why does my database keep growing in size?
It depends entirely on what you are doing with the data. For basic insert/update/delete transactions that affect just a few rows, then the growth in data size is probably not a big consideration. The database will use in-memory indexes to access the correct page. You get more cache misses when the tables no longer fit into memory.
How does the size of a table affect performance?
Smaller tables normally require less main memory while their contents are being actively processed during query execution. Any space reduction for table data also results in smaller indexes that can be processed faster.
How does MySQL reduce the size of a table?
Smaller tables normally require less main memory while their contents are being actively processed during query execution. Any space reduction for table data also results in smaller indexes that can be processed faster. MySQL supports many different storage engines (table types) and row formats.