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11 lip 2014 · Turn the EXISTS clause into a subquery instead within an IF function. SELECT IF( EXISTS( SELECT * FROM gdata_calendars WHERE `group` = ? AND id = ?), 1, 0) In fact, booleans are returned as 1 or 0. SELECT EXISTS( SELECT * FROM gdata_calendars WHERE `group` = ? AND id = ?)
The IFNULL() function returns a specified value if the expression is NULL. If the expression is NOT NULL, this function returns the expression. Syntax
The EXISTS operator is used to test for the existence of any record in a subquery. The EXISTS operator returns TRUE if the subquery returns one or more records. Below is a selection from the "Products" table in the Northwind sample database: And a selection from the "Suppliers" table:
MySQL ignores the SELECT list in such a subquery, so it makes no difference. For the preceding example, if t2 contains any rows, even rows with nothing but NULL values, the EXISTS condition is TRUE .
3 sty 2023 · Basic Usage of the EXISTS Operator in MySQL. The EXISTS condition in MySQL is generally used along with a subquery that consists of a condition to be met. If this condition is met, then the subquery returns a minimum of one row. This method can be used to DELETE, SELECT, INSERT, or UPDATE a statement.
If outer_expr is NULL, to evaluate the following expression, it is necessary to execute the SELECT to determine whether it produces any rows: NULL IN (SELECT inner_expr FROM ... WHERE subquery_where)
27 maj 2021 · You'll want to use an OUTER JOIN, such as a LEFT OUTER JOIN (LEFT JOIN for short) to accomplish your goal, something like this: a1.ticket_id AS 'ticket_id', a2.data_content AS 'category_ticket_1', a3.data_content AS 'category_ticket_2' ON a1.ticket_id = a2.ticket_id. AND a2.field_name_id = "category_ticket_1" ON a1.ticket_id = a3.ticket_id.
