If not exists mysql

The DUAL table is a special one-row, one-column table present by default in Oracle and other database installations. ON DUPLICATE KEY UPDATE will. So you can use the mysql_num_rows function to know how many. IF NOT EXISTS statements are replicated: Every CREATE DATABASE IF NOT EXISTS statement is replicate whether or not the database already exists on the master.

For the preceding example, if tcontains any rows, even rows with nothing but NULL values, the EXISTS condition is TRUE.

Insert Into table If similar value exists in another existing table ( not a foreign key) 0. Update or Insert with where clause. The SQL EXISTS Operator. MySQL IF EXISTS not working. SELECT name FROM eotm_dyn WHERE eotm_dyn.

The EXISTS operator returns true if the subquery returns one or more records. This means that an INSERT IGNORE statement which contains a duplicate value in a UNIQUE index or PRIMARY KEY field does not produce an error, but will instead simply ignore that particular INSERT command entirely.

INSERT IGNORE is nonstandard SQL, but often quite useful, particularly when you are writing app-level “crash recovery” code. EXISTS and NOT EXISTS are used with a subquery in WHERE clause to examine if the result the subquery returns is TRUE or FALSE. The true or false value is then used to restrict the rows from outer query select. I will select name from table where name is the same name I want to insert.

The “ NOT EXISTS ” statement uses a subquery to filter out records that do not exist in the underlying subquery. This logic is sometimes hard to grasp for new SQL coders, but this article explains the logic and alternatives to the NOT EXISTS statement. The exists condition can be used with subquery. It returns true when row exists in the table, otherwise false is returned.

My query would give you the count of indexes present on a table with a particular index_name. Based on that count, you can decide whether to issue a CREATE INDEX command or not. MariaDB supports IF NOT EXISTS syntax.

You can use CREATE INDEX IF NOT EXISTS there. If a record where KEY_ATTR = 1is already there, the above query will not insert a recor otherwise it will. This works best if there is an index on KEY_ATTR as well.

In this article I’ll explain several ways to write such queries in a platform-independent way. Then you could continue on and insert that id into another table or what have you.

Let us verify the concept. The table name DemoTable is already present. Table created successfully above since it does not already exist. In your link: Data conversions that would trigger errors abort the statement if IGNORE is not specified. It may not be the best choice.

Tested on MySQL version 5. Here is an example of the type of query that can be optimized this way: Assume that t2. The NOT EXISTS in SQL Server will check the Subquery for rows existence, and if there are no rows then it will return TRUE, otherwise FALSE. Or we can simply say, SQL Server Not Exists operator will return the exactly opposite to the result returned by the Subquery.