Presto: SQL over big data, NoSQL and relational DBMS
What about using SQL to retrieve data from NoSQL databases? Or to make joins between tables stored in relational databases[…]
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Tag: SQL
Using Sequences in database systems
A Sequence is a database object capable to generate numbers (i.e. it is a number generator). One of the main[…]
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SQL Count(*), Count(cte), Count(column), Count(pk), … x Inner and Outer Joins
In SQL, The Count function counts the number of values in a set. Such function accepts a parameter, that specifies[…]
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How to delete millions of rows from a table
To delete a great number of rows from a table may become a pain in the neck. A never ending[…]
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SQL: 3 ways to find gaps and missing values
It is really common to have columns that stores sequences of numbers in database systems (specially in relational databases). Users[…]
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SQL: from [Not] In to [Not] Exists in 3 steps
For many people, using noncorrelated subqueries (using In/Not In) seems to be more natural than using Exists/Not Exists and correlated[…]
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SQL Inner and (Left/Right/Full) Outer Joins
Joins are one of the most common operators in SQL queries. In this post, we present inner and outer joins[…]
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Autonomous Transactions
Transaction management is a key functionality of database management systems (DBMS). Its main properties include Atomicity, Consistency, Isolation and Durability[…]
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Database Tuning, SQL Execution Plan and Query Rewrite
In a previous post, we present an introduction to database tuning. In this post, we’ll talk about SQL execution plans[…]
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3 ways to remove duplicate data
Duplicate data can be generated in the database due to design error, software bugs or misuse by end users. Depending[…]
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