Something that now and then are always needed, the SQL queries to get the list of table names from a database, or the column names for a table.
Below are the queries for MySQL, PostgreSQL and Microsoft SQL server.
MySQL
To get the table list:
show tables;
To get the column list for a table:
show columns from <tableName>;
PostgreSQL
To get the table list:
SELECT table_name FROM information_schema.tables WHERE table_catalog ='<dbName>' and table_schema = 'public';
To get the column list for a table:
SELECT column_name FROM information_schema.columns where table_catalog = '<dbName>' and table_name = '<tableName>';
SQL Server
To get the table list:
SELECT TABLE_NAME FROM <dbName>.INFORMATION_SCHEMA.Tables;
To get the column list for a table:
SELECT COLUMN_NAME FROM <dbName>.INFORMATION_SCHEMA.COLUMNS WHERE TABLE_NAME = '<tableName>';