<\/span><\/h2>\nOne of the most basic and essential functions in SQL is querying data using the SELECT statement. This function allows us to select and retrieve data from a table or set of tables in a database. We can specify the fields we want to retrieve, as well as apply conditions and filters using clauses such as WHERE and ORDER BY.<\/p>\n
For example, if we want to get the names and ages of all users over 18 years old from a table called "users", we can use the following query:<\/p>\n
\nSELECT name, age FROM users WHERE age > 18;\n<\/pre>\nThere are many other clauses and operators that can be used in conjunction with SELECT to perform more complex data queries, such as JOIN, GROUP BY, HAVING, among others.<\/p>\n
<\/span>Inserting data with INSERT<\/span><\/h2>\nAnother important function in SQL is inserting data into a table. The INSERT statement allows us to add records to a specific table, specifying the values for each column. For example, if we have a table called "customers" with the columns "name" and "email", we can use the following query to add a new customer:<\/p>\n
\nINSERT INTO clients (name, email) VALUES ('John Doe', 'johndoe@gmail.com');\n<\/pre>\nIt is important to note that we must specify the values in the same order as the columns in the table. Additionally, we can use the INSERT statement in conjunction with the SELECT statement to insert data from another table.<\/p>\n
<\/span>Updating data with UPDATE<\/span><\/h2>\nThe UPDATE statement allows us to update the values of one or more columns in existing records in a table. This is useful when we want to modify specific information in our databases. For example, if we want to update the name of a user in a table called "users", we can use the following query:<\/p>\n
\nUPDATE users SET name = 'Jane Doe' WHERE id = 1;\n<\/pre>\nIt is important to specify the condition using the WHERE clause to indicate which records should be updated.<\/p>\n
<\/span>Deleting data with DELETE<\/span><\/h2>\nThe DELETE statement allows us to delete records from a table in a database. This feature is useful when we want to delete information that is no longer relevant or does not meet certain criteria. For example, if we want to remove all users under 18 from a table called "users", we can use the following query:<\/p>\n
\nDELETE FROM users WHERE age < 18;\n<\/pre>\nIt is important to be careful when using the DELETE statement, as it can permanently delete data.<\/p>\n
<\/span>Other useful functions<\/span><\/h2>\nIn addition to the main functions mentioned above, SQL has a wide variety of other functions that allow us to perform more specific actions, such as:<\/p>\n