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ClickHouse was designed for OLAP queries. [5] ClickHouse performs well when: It works with a small number of tables that contain a large number of columns. Queries use a large number of rows extracted from the DB, but only a small subset of columns. Queries are relatively rare (usually around 100 requests per second per server).
SQL LINQ [19] Visualization JSON REST API; Apache Doris No No No No Yes [20] Yes No Superset, Redash, Metabase, Tableau, Qlik, Pivot, PowerBI Yes Yes Apache Druid: No No No No Yes Druid SQL No Superset, Pivot, Redash Yes Yes Apache Kylin: Yes No Yes No Yes Yes Superset, Zeppelin, Tableau, Qlik, Redash, Microsoft Excel Yes Yes Apache Pinot: No ...
SQLAlchemy is an open-source Python library that provides an SQL toolkit (called "SQLAlchemy Core") and an Object Relational Mapper (ORM) for database interactions. It allows developers to work with databases using Python objects, enabling efficient and flexible database access.
In essence, each action of slicing and dicing is equivalent to adding a "WHERE" clause in the SQL statement. ROLAP tools do not use pre-calculated data cubes but instead pose the query to the standard relational database and its tables in order to bring back the data required to answer the question.
In SQL:1999 a recursive (CTE) query may appear anywhere a query is allowed. It's possible, for example, to name the result using CREATE [RECURSIVE] VIEW. [16] Using a CTE inside an INSERT INTO, one can populate a table with data generated from a recursive query; random data generation is possible using this technique without using any ...
Example: using logging_userindex instead of logging. Sub-views - The replica databases (used by Quarry) have copies of certain tables that omit unnecessary rows. Look into using these tables instead of the main table when joining certain tables, to speed up your queries. Example: When joining actor and recentchanges, use actor_recentchanges.
An ORDER BY clause in SQL specifies that a SQL SELECT statement returns a result set with the rows being sorted by the values of one or more columns. The sort criteria does not have to be included in the result set (restrictions apply for SELECT DISTINCT, GROUP BY, UNION [DISTINCT], EXCEPT [DISTINCT] and INTERSECT [DISTINCT].)
Conjunctive queries without distinguished variables are called boolean conjunctive queries.Conjunctive queries where all variables are distinguished (and no variables are bound) are called equi-join queries, [1] because they are the equivalent, in the relational calculus, of the equi-join queries in the relational algebra (when selecting all columns of the result).