数据库值插入错误

Question

How can i manually insert values if not exist...i tried following code but it produce error.How can i insert values if not exist in the table

 String sql1 = "CREATE TABLE IF NOT EXISTS admin " +
                    "(id INTEGER not NULL AUTO_INCREMENT, " +
                    " user_name VARCHAR(255), " + 
                    " password VARCHAR(255), " + 
                    " isAdmin BOOLEAN NOT NULL DEFAULT '0', " + 
                    " memo VARCHAR(255), " + 
                    " PRIMARY KEY ( id ))"; 
            stmt.executeUpdate(sql1);

            String insert="INSERT INTO admin IF NOT EXISTS(id,user_name,password,isAdmin,memo)VALUES(1,'admin','admin',1,'memo')";
            stmt.executeUpdate(insert);

it produce an error like

 com.mysql.jdbc.exceptions.jdbc4.MySQLSyntaxErrorException: You have an error in your SQL syntax; check the manual that corresponds to your MySQL server version for the right syntax to use near 'IF NOT EXISTS(id,user_name,password,isAdmin,memo)VALUES(1,'admin','admin',1,'mem' at line 1
at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)

Answer 1

 String insert="INSERT INTO admin IF NOT EXISTS(id,user_name,password,isAdmin,memo)VALUES(1,'admin','admin',1,'memo')";

应该

 String insert="INSERT IGNORE INTO admin (id,user_name,password,isAdmin,memo)VALUES(1,'admin','admin',1,'memo')";

Answer 2

MySQL (and any other SQL implementation as well) doesn't support IF NOT EXISTS in INSERT queries.

your INSERT query must be

"INSERT IGNORE INTO admin (id,user_name,password,isAdmin,memo) VALUES (1,'admin','admin',1,'memo')"

Answer 3

What you want may be INSERT ... ON DUPLICATE KEY UPDATE or INSERT IGNORE... .

The former will update an existing row if a duplicate insert is detected, while the latter will just throw away duplicate inserts.

In both cases, you'll have to create a UNIQUE constraint on the column you want to check for duplicates. If the UNIQUE is violated, the alternate function is invoked.