What is the difference between WHERE and HAVING clauses?

https://www.essentialsql.com/what-is-the-difference-between-where-and-having-clauses/ In fact, their functions complement each other. A WHERE clause is used is filter records from a result. The filter occurs before any groupings are made. A HAVING clause is used to filter values from a group. That means the WHERE clause is first applied to the result and then, the remaining rows summarized ...

PostgreSQL: How to Disable or Enable Foreign Key Constraint of a Table

https://www.dbrnd.com/2017/02/postgresql-how-to-disable-or-enable-foreign-key-constraint-of-a-table-data-migration-bulk-operation/ ALTER TABLE table_name DISABLE TRIGGER ALL; INSERT INTO table_name VALUES (1,6,50,60,90); ALTER TABLE table_name ENABLE TRIGGER ALL;

UUID Primary Keys in PostgreSQL

http://www.starkandwayne.com/blog/uuid-primary-keys-in-postgresql/ https://dba.stackexchange.com/questions/146135/psql-9-5-gen-random-uuid-not-working psql 9.5: gen_random_uuid() not working? SELECT gen_random_uuid() produces output: ERROR: function gen_random_uuid() does not exist SQL state: 42883 Hint: No function matches the given name and argument types. You might need to add explicit type casts. you can check if the functions are defined using: select * from pg_proc where proname like ‘gen_random_%’; ...

The difference between a unique index and primary key in MySQL


Dlaczego w MySQL’u nie stosować typu FLOAT

http://www.dobreprogramy.pl/slepciu/Dlaczego-w-MySQLu-nie-stosowac-typu-FLOAT,30401.html http://doctrine-dbal.readthedocs.org/en/latest/reference/types.html#decimal-types http://doctrine-orm.readthedocs.org/en/latest/reference/basic-mapping.html

Problem during MySql update from 5.5 to 5.6 version

When you encountered the error message: mysql-server-5.6 : Depends: mysql-client-5.6 (>= 5.6.19-1~dotdeb.1) but it is not going to be installed during MySql update from 5.5 to 5.6 version, you should do: sudo apt-get install mysql-common=5.6.19-1~dotdeb.1 You can also check all available version with: sudo apt-cache showpkg mysql-common

How to set auto increment jumps by more than the number of rows inserted?

http://dev.mysql.com/doc/refman/5.6/en/replication-options-master.html#sysvar_auto_increment_increment auto_increment_increment and auto_increment_offset are intended for use with master-to-master replication, and can be used to control the operation of AUTO_INCREMENT columns.

MySQL: “Access denied for user ‘debian-sys-maint’@’localhost’”


How to safely change MySQL innodb variable ‘innodb_log_file_size’?

http://dba.stackexchange.com/questions/1261/how-to-safely-change-mysql-innodb-variable-innodb-log-file-size innodb_log_file_size = 25% * innodb_buffer_pool_size, np: [mysqld] innodb_log_file_size = 64M

Jaka wielkość innodb_buffer_pool_size będzie optymalna?

http://blog.suszalski.pl/2011/03/jaka-wielkosc-innodbbufferpoolsize.html innodb_buffer_pool_size < 80% RAM, np: [mysqld] innodb_buffer_pool_size = 512M