I have developed four series of useful SQL tips and tricks in this context.
Each series will contain a list of 25 set of tips and tricks among which I am releasing the first one here. If you have any other tips and tricks that I failed to mention, please post me on hioraclemine gmail. Integrity rules do not pass to the new table.
Syntax of Procedure. It sometimes degrades the performance.
2. The * Operator
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SQL Tips, Tricks, & Techniques
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10 SQL Tricks That You Didn’t Think Were Possible – Java, SQL and jOOQ.
Notify me of follow-up comments by email. Notify me of new posts by email. Name, Sales. In a Cartesian Join, all possible combinations of the variables are created. In this example, if we had 1, customers with 1, total sales, the query would first generate 1,, results, then filter for the 1, records where CustomerID is correctly joined. This is an inefficient use of database resources, as the database has done x more work than required.
1. Everything is a Table
Cartesian Joins are especially problematic in large-scale databases, because a Cartesian Join of two large tables could create billions or trillions of results. Your DBA will advise you as to which is best in your environment. Similar to the above mentioned concept, the goal of an efficient query is to pull only the required records from the database.
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Name, Count Sales. This query would pull 1, sales records from the Sales table, then filter for the records generated in the year , and finally count the records in the dataset. This query would pull the records from the year , and then count the records in the dataset. When searching plaintext data, such as cities or names, wildcards create the widest search possible.
However, the widest search is also the most inefficient search. When a leading wildcard is used, especially in combination with an ending wildcard, the database is tasked with searching all records for a match anywhere within the selected field. This query will pull the expected results of Char leston, Char lotte, and Char lton.source url
Query optimization techniques in SQL Server: tips and tricks
However, it will also pull unexpected results, such as Cape Char les, Crab Or char d, and Rich ardson. This query will pull only the expected results of Char leston, Char lotte, and Char lton.
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Before running a query for the first time, ensure the results will be desirable and meaningful by using a LIMIT statement. Using a LIMIT statement prevents taxing the production database with a large query, only to find out the query needs editing or refinement. In order to minimize query impact on the production database, talk to a DBA about scheduling the query to run at an off-peak time. The query should run when concurrent users are at their lowest number, which is typically the middle of the night 3 — 5 a.
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