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SQL 🔥

SQL Interview Questions 👆

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SQL, or Structured Query Language, is a domain-specific language used to manage and manipulate relational databases. A - Aggregate Functions: Functions like COUNT, SUM, AVG, MIN, and MAX used to perform operations on data in a database. B - BETWEEN: A SQL operator used to filter results within a specific range. C - CREATE TABLE: SQL statement for creating a new table in a database. D - DELETE: SQL statement used to delete records from a table. E - EXISTS: SQL operator used in a subquery to test if a specified condition exists. F - FOREIGN KEY: A field in a database table that is a primary key in another table, establishing a link between the two tables. G - GROUP BY: SQL clause used to group rows that have the same values in specified columns. H - HAVING: SQL clause used in combination with GROUP BY to filter the results. I - INNER JOIN: SQL clause used to combine rows from two or more tables based on a related column between them. J - JOIN: Combines rows from two or more tables based on a related column. K - KEY: A field or set of fields in a database table that uniquely identifies each record. L - LIKE: SQL operator used in a WHERE clause to search for a specified pattern in a column. M - MODIFY: SQL command used to modify an existing database table. N - NULL: Represents missing or undefined data in a database. O - ORDER BY: SQL clause used to sort the result set in ascending or descending order. P - PRIMARY KEY: A field in a table that uniquely identifies each record in that table. Q - QUERY: A request for data from a database using SQL. R - ROLLBACK: SQL command used to undo transactions that have not been saved to the database. S - SELECT: SQL statement used to query the database and retrieve data. T - TRUNCATE: SQL command used to delete all records from a table without logging individual row deletions. U - UPDATE: SQL statement used to modify the existing records in a table. V - VIEW: A virtual table based on the result of a SELECT query. W - WHERE: SQL clause used to filter the results of a query based on a specified condition. X - (E)XISTS: Used in conjunction with SELECT to test the existence of rows returned by a subquery. Z - ZERO: Represents the absence of a value in numeric fields or the initial state of boolean fields.

SQL Essential Concepts 𝟭. 𝗜𝗻𝘁𝗿𝗼 𝘁𝗼 𝗦𝗤𝗟: Definition, purpose, relational DBs, DBMS. 𝟮. 𝗕𝗮𝘀𝗶𝗰 𝗦𝗤𝗟 𝗦𝘆𝗻𝘁𝗮𝘅: SELECT, FROM, WHERE, ORDER BY, GROUP BY. 𝟯. 𝗗𝗮𝘁𝗮 𝗧𝘆𝗽𝗲𝘀: Integer, floating-point, character, date, VARCHAR, TEXT, BLOB, BOOLEAN. 𝟰. 𝗦𝘂𝗯 𝗹𝗮𝗻𝗴𝘂𝗮𝗴𝗲𝘀: DML, DDL, DQL, DCL, TCL. 𝟱. 𝗗𝗮𝘁𝗮 𝗠𝗮𝗻𝗶𝗽𝘂𝗹𝗮𝘁𝗶𝗼𝗻: INSERT, UPDATE, DELETE. 𝟲. 𝗗𝗮𝘁𝗮 𝗗𝗲𝗳𝗶𝗻𝗶𝘁𝗶𝗼𝗻: CREATE, ALTER, DROP, Indexes. 𝟳. 𝗤𝘂𝗲𝗿𝘆 𝗙𝗶𝗹𝘁𝗲𝗿𝗶𝗻𝗴 𝗮𝗻𝗱 𝗦𝗼𝗿𝘁𝗶𝗻𝗴: WHERE, AND, OR conditions, ascending, descending. 𝟴. 𝗗𝗮𝘁𝗮 𝗔𝗴𝗴𝗿𝗲𝗴𝗮𝘁𝗶𝗼𝗻: SUM, AVG, COUNT, MIN, MAX. 𝟵. 𝗝𝗼𝗶𝗻𝘀 𝗮𝗻𝗱 𝗥𝗲𝗹𝗮𝘁𝗶𝗼𝗻𝘀𝗵𝗶𝗽𝘀: INNER JOIN, LEFT JOIN, RIGHT JOIN, Self-Joins, Cross Joins, FULL OUTER JOIN. 𝟭𝟬. 𝗦𝘂𝗯𝗾𝘂𝗲𝗿𝗶𝗲𝘀: Filtering data, aggregating data, joining tables, correlated subqueries. 𝟭𝟭. 𝗩𝗶𝗲𝘄𝘀: Creating, modifying, dropping views. 𝟭𝟮. 𝗧𝗿𝗮𝗻𝘀𝗮𝗰𝘁𝗶𝗼𝗻𝘀: ACID properties, COMMIT, ROLLBACK, SAVEPOINT, ROLLBACK TO SAVEPOINT. 𝟭𝟯. 𝗦𝘁𝗼𝗿𝗲𝗱 𝗣𝗿𝗼𝗰𝗲𝗱𝘂𝗿𝗲𝘀: CREATE, ALTER, DROP, EXECUTE, User-Defined Functions (UDFs). 𝟭𝟰. 𝗧𝗿𝗶𝗴𝗴𝗲𝗿𝘀: Trigger events, trigger execution, and syntax. 𝟭𝟱. 𝗦𝗲𝗰𝘂𝗿𝗶𝘁𝘆 𝗮𝗻𝗱 𝗣𝗲𝗿𝗺𝗶𝘀𝘀𝗶𝗼𝗻𝘀: CREATE USER, GRANT, REVOKE, ALTER USER, DROP USER. 𝟭𝟲. 𝗢𝗽𝘁𝗶𝗺𝗶𝘇𝗮𝘁𝗶𝗼𝗻𝘀: Indexing strategies, query optimization. 𝟭𝟳. 𝗡𝗼𝗿𝗺𝗮𝗹𝗶𝘇𝗮𝘁𝗶𝗼𝗻: 1NF, 2NF, 3NF, BCNF. 𝟭𝟴. 𝗡𝗼𝗦𝗤𝗟 𝗗𝗮𝘁𝗮𝗯𝗮𝘀𝗲𝘀: MongoDB, Cassandra, and key differences. 𝟭𝟵. 𝗗𝗮𝘁𝗮 𝗜𝗻𝘁𝗲𝗴𝗿𝗶𝘁𝘆: Primary key, foreign key. 𝟮𝟬. 𝗔𝗱𝘃𝗮𝗻𝗰𝗲𝗱 𝗦𝗤𝗟 𝗤𝘂𝗲𝗿𝗶𝗲𝘀: Window functions, Common Table Expressions (CTES).

tar command - how to archive files in Linux The tar command in Linux is a go-to tool for creating backups, bundling files, and compressing archives. Short for tape archive, tar lets you group files into archives commonly called tarballs and compress them using algorithms like gzip, bzip2, and xz. If you’re packaging software or simply managing file storage, tar is a powerful tool to have in your Linux toolkit.

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