Databases In MongoDB In MongoDB the databases are divided in to two types based on the data they store they are. 1. Default databases 2. Non default databases Non default databases: The databases that are created explicitly depend on the needs of the users. Default… Read More
Remote Connections in PostgreSQL: Remote connections will allow you to connect to a PostgreSQL server from a different machine or network. In this article, we will explore the steps to establish remote connections in PostgreSQL and provide best practices for securing these connections. This article… Read More
MongoDB Commands On Operators To create a collection called student data.
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Atlas atlas-dsrabt-shard-0 [primary] practisedata> db.createCollection("studentdata") |
To get all the documents in a collection called student data without any filter.
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Atlas atlas-dsrabt-shard-0 [primary] practisedata> db.studentdata.find() |
To get all the documents whose total marks is equals to 560.
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Atlas atlas-dsrabt-shard-0 [primary] practisedata> db.studentdata.find({totalmarks:{$eq:560}}) |
To get all the documents… Read More
ENVIRONMENT VARIABLES IN PostgreSQL: These are useful to avoid hard-coding database connection information into simple client applications, for example. To start a PostgreSQL server, you can run the following command:
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[postgres@postgres1 ~]$ /usr/local/pgsql/bin/pg_ctl –D /u01/data start |
However, you can also use an environmental variable to create a shortcut for this… Read More
CLUSTER AND MULTICLUSTERS IN POSTGRESQL: In PostgreSQL Before you can start a PostgreSQL server, you need to create a cluster. A cluster refers to a collection of databases managed by a single instance of the PostgreSQL server. When you install PostgreSQL, It doesn’t automatically create… Read More
MongoDB Query Operators Part-3 Evaluation Query Operators MongoDB Evaluation operators are used to evaluate the structure of overall data or the individual fields in the document. They are of six types of Evaluations operators 1. mod ($mod) 2. text ($text) 3. where ($where) 4. jsonSchema… Read More
MongoDB Query Operators Part-2 Element Query Operator This operator is used to find the documents based on the datatypes and the fields in a document. There are two element query operators. 1. exists ($exists) 2. type ($type) 1. exist ($exist): This operator is used to… Read More
Clauses and filters: Like clause:
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college=# select * from report where temp_hi:: text like '4%'; place | temp_lo | temp_hi | date | humidity | precp ----------------------------------------------------------- VZG | 32 | 43 | 2023-05-10 | 21 | HYD | 32 | 43 | 2020-07-19 | 24 | BZA | 32 | 43 | 2023-05-09 | 23 | (3 rows) |
LIMIT Clause: The LIMIT clause is used to restrict the number of rows returned in the result set. It is useful when you want to retrieve only a certain number of rows.
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college=# select * from report LIMIT 4; place | temp_lo | temp_hi | date | humidity | precp ----------------------------------------------------------- VZG | 32 | 43 | 2023-05-10 | 21 | HYD | 32 | 43 | 2020-07-19 | 24 | BZA | 32 | 43 | 2023-05-09 | 23 | Delhi | 23 | 34 | 2023-05-15 | 24 | (4 rows) |
OFFSET Clause: It is used in conjunction… Read More
JOIN OPERATION IN PostgreSQL: In PostgreSQL, the JOIN clause is used to combine rows from two or more tables based on a related column or condition. It specifies how the tables should be joined and on which columns the join should be performed. There are… Read More
MongoDB Query Operators There are different types of Operators available in MongoDB which are used to filter the data. 1 – Comparison operators 2 – Logical operators 3 – Element operators 4 – Evaluation operators 5 – Geospatial operators 6 – Array operators 7 –… Read More
