What is WHERE clause in MySQL?
Description. The MySQL WHERE clause is used to filter the results from a SELECT, INSERT, UPDATE, or DELETE statement.
What is the purpose of WHERE clause in MySQL?
WHERE Clause in MySQL is a keyword used to specify the exact criteria of data or rows that will be affected by the specified SQL statement. The WHERE clause can be used with SQL statements like INSERT, UPDATE, SELECT, and DELETE to filter records and perform various operations on the data.
Can we use case in WHERE clause in MySQL?
MySQL CASE expression is a control flow structure that allows you to add if-else logic to a query. Generally speaking, you can use the CASE expression anywhere that allows a valid expression e.g., SELECT , WHERE and ORDER BY clauses. The CASE expression has two forms: simple CASE and searched CASE .
How does WHERE work in MySQL?
MySQL – WHERE Clause
- You can use one or more tables separated by a comma to include various conditions using a WHERE clause, but the WHERE clause is an optional part of the SELECT command.
- You can specify any condition using the WHERE clause.
- You can specify more than one condition using the AND or the OR operators.
Can we use WHERE and having clause together?
A query can contain both a WHERE clause and a HAVING clause. In that case: Only the rows that meet the conditions in the WHERE clause are grouped. The HAVING clause is then applied to the rows in the result set.
Can we use case when in where clause?
CASE can be used in any statement or clause that allows a valid expression. For example, you can use CASE in statements such as SELECT, UPDATE, DELETE and SET, and in clauses such as select_list, IN, WHERE, ORDER BY, and HAVING.
How do I use Isnull in MySQL?
If expr is NULL , ISNULL() returns 1 , otherwise it returns 0 . ISNULL() can be used instead of = to test whether a value is NULL ….Table 12.4 Comparison Operators.
| Name | Description |
|---|---|
| IS NOT | Test a value against a boolean |
| IS NOT NULL | NOT NULL value test |
| IS NULL | NULL value test |
| ISNULL() | Test whether the argument is NULL |
What is count () in MySQL?
MySQL count() function is used to returns the count of an expression. It allows us to count all rows or only some rows of the table that matches a specified condition. It is a type of aggregate function whose return type is BIGINT.
Which command is used to add a row?
INSERT INTO `table_name` is the command that tells MySQL server to add a new row into a table named `table_name. `…Example:
| Full names | Howard Wolowitz |
|---|---|
| Date of Birth | 24/08/1981 |
| gender | Male |
| Physical address | South Park |
| Contact number | 0987786553 |