Postgres 12 or newer STORED generated columns are introduced with Postgres 12 – as defined in the SQL standard and implemented by some RDBMS including DB2, MySQL, and Oracle. Or the similar “computed columns” of SQL Server. Trivial example: CREATE TABLE tbl ( int1 int , int2 int , product bigint GENERATED ALWAYS AS (int1 … Read more
Search Tables: SELECT c.name AS ‘ColumnName’ ,(SCHEMA_NAME(t.schema_id) + ‘.’ + t.name) AS ‘TableName’ FROM sys.columns c JOIN sys.tables t ON c.object_id = t.object_id WHERE c.name LIKE ‘%MyName%’ ORDER BY TableName ,ColumnName; Search Tables and Views: SELECT COLUMN_NAME AS ‘ColumnName’ ,TABLE_NAME AS ‘TableName’ FROM INFORMATION_SCHEMA.COLUMNS WHERE COLUMN_NAME LIKE ‘%MyName%’ ORDER BY TableName ,ColumnName;
The most general difference between procedures and functions is that they are invoked differently and for different purposes: A procedure does not return a value. Instead, it is invoked with a CALL statement to perform an operation such as modifying a table or processing retrieved records. A function is invoked within an expression and returns … Read more
Because the number can be up to 15 digits, you’ll need to cast to an 64 bit (8-byte) integer. Try this: SELECT * FROM table WHERE myint = mytext::int8 The :: cast operator is historical but convenient. Postgres also conforms to the SQL standard syntax myint = cast ( mytext as int8) If you have … Read more
I’m going to add a somewhat longer and more detailed explanation of the steps to take to solve this problem. I apologize if it’s too long. I’ll start out with the base you’ve given and use it to define a couple of terms that I’ll use for the rest of this post. This will be … Read more
I accomplished the same goal by using a WITH clause, it’s nowhere near as elegant but can do the same thing. Though for this example it’s really overkill. I also don’t particularly recommend this. WITH myconstants (var1, var2) as ( values (5, ‘foo’) ) SELECT * FROM somewhere, myconstants WHERE something = var1 OR something_else … Read more
You want to find top n rows per group. This answer provides a generic solution using example data that is different from OP. In MySQL 8 or later you can use the ROW_NUMBER, RANK or DENSE_RANK function depending on the exact definition of top 5. Below are the numbers generated by these functions based on … Read more
You can do with the –no-data option with mysqldump command mysqldump -h yourhostnameorIP -u root -p –no-data dbname > schema.sql
They are not the same thing. Consider these queries: SELECT * FROM Orders LEFT JOIN OrderLines ON OrderLines.OrderID=Orders.ID WHERE Orders.ID = 12345 and SELECT * FROM Orders LEFT JOIN OrderLines ON OrderLines.OrderID=Orders.ID AND Orders.ID = 12345 The first will return an order and its lines, if any, for order number 12345. The second will return … Read more
SELECT name, email, COUNT(*) FROM users GROUP BY name, email HAVING COUNT(*) > 1 Simply group on both of the columns. Note: the older ANSI standard is to have all non-aggregated columns in the GROUP BY but this has changed with the idea of “functional dependency”: In relational database theory, a functional dependency is a … Read more