Just set a unique index on composite of (username, date). ALTER TABLE `table` ADD UNIQUE INDEX `name` (`username`, `date`); Alternatively, you can try to ALTER TABLE `table` DROP PRIMARY KEY, ADD PRIMARY KEY(`username`,`date`); and I think in the latter case you need those columns to be declared NOT NULL.
ALTER TABLE table_name AUTO_INCREMENT=310; Beware though, you don’t want to repeat an ID. If the numbers are that high, they got that way somehow. Be very sure you don’t have associated data with the lower ID numbers. https://dev.mysql.com/doc/refman/8.0/en/example-auto-increment.html
Postgres 10 or later Consider a standard-SQL IDENTITY column. serial columns remain unchanged. (See below.) But the former is preferable in modern Postgres. Can be GENERATED BY DEFAULT or (stricter) GENERATED ALWAYS. Basics in the manual for CREATE TABLE. Details in this blog entry by its principal author Peter Eisentraut. Create table with IDENTITY column … Read more
Use a prepared statement: SELECT @max := MAX(ID)+ 1 FROM ABC; PREPARE stmt FROM ‘ALTER TABLE ABC AUTO_INCREMENT = ?’; EXECUTE stmt USING @max; DEALLOCATE PREPARE stmt;
Normally Sequelize.js adapt itself with the database. So the autoincrement attribute corresponds to a serial type in PostgreSQL. I already worked with Sequelize and what I remember is that you don’t need to specify an id as a primary key. Sequelize will do it for you. Try to not add an id attribute and see … Read more
You could modify your INSERT to be something like this: INSERT INTO tablename (tag) SELECT $tag FROM tablename WHERE NOT EXISTS( SELECT tag FROM tablename WHERE tag = $tag ) LIMIT 1 Where $tag is the tag (properly quoted or as a placeholder of course) that you want to add if it isn’t already there. … Read more
Converting an int to a serial more or less only means adding a sequence default to the value, so to make it a serial; Pick a starting value for the serial, greater than any existing value in the table SELECT MAX(id)+1 FROM mytable Create a sequence for the serial (tablename_columnname_seq is a good name) CREATE … Read more
num += 1 is rather equivalent to ++num. All those expressions (num += 1, num++ and ++num) increment the value of num by one, but the value of num++ is the value num had before it got incremented. Illustration: int a = 0; int b = a++; // now b == 0 and a == … Read more
It works for me. JDBC URL: jdbc:h2:~/temp/test2 drop table test; create table test(id bigint auto_increment, name varchar(255)); insert into test(name) values(‘hello’); insert into test(name) values(‘world’); select * from test; result: ID NAME 1 hello 2 world
UUIDs Unless these are generated “in increasing monotonic sequence” they can drastically hurt/fragment indexes. Support for UUID generation varies by system. While usable, I would not use a UUID as my primary clustered index/PK in most cases. If needed I would likely make it a secondary column, perhaps indexed, perhaps not. Some people argue that … Read more