In SQL, the COUNT() function is an aggregate function that returns the number of items found in a group.
You can use COUNT() in multiple parts of a query. For example, you can use it in the SELECT list, or the HAVING clause when filtering groups.
In SQL, the HAVING clause can be used to specify a search condition for a group or an aggregate.
The HAVING clause is typically used with the GROUP BY clause. In cases where it’s not, there is an implicit single, aggregated group.
The SELECT statement is almost without doubt, the most commonly used statement in SQL.
The SELECT statement is used for retrieving data from the database. You can specify which rows you want returned, and which columns.
In SQL, the GROUP BY clause can be used to divide the results of a query into groups of rows.
This is usually done in order to perform one or more aggregations on each group.
Continue readingThe ORDER BY clause is commonly used in SQL to sort the results of a query.
It allows you to specify the order in which the results are returned.
You can specify whether the results are sorted in ascending order or descending order. You can also specify multiple columns for sorting.
Continue readingIn SQL, transactions are used to maintain data integrity by ensuring that a sequence of SQL statements execute completely or not at all.
Transactions manage sequences of SQL statements that must be executed as a single unit of work, so that the database never contains the results of partial operations.
When a transaction makes multiple changes to the database, either all the changes succeed when the transaction is committed, or all the changes are undone when the transaction is rolled back.
Continue readingIn SQL, the greater than operator (>) compares two expressions and returns TRUE if the left operand has a value higher than the right operand; otherwise, it returns FALSE.
In SQL, the greater than or equal to operator (>=) compares two expressions and returns TRUE if the left operand has a value greater than or equal to the right operand; otherwise, it returns FALSE.
In SQL, the less than or equal to operator (<=) compares two expressions and returns TRUE if the left operand has a value lower than or equal to the right operand; otherwise, the result is FALSE.
You can use it to determine whether a value is less than or equal to another value.
Continue readingIn SQL, the less than operator (<) compares two expressions and returns TRUE if the left operand has a value lower than the right operand; otherwise, the result is FALSE.