t1 has all the credits of each person in a given ORACLE database. Each person is identified by ID. t2 contains the people I need to select from t1. To do this, I tried the following: My problem is that t2 has duplicate IDs. So for example, if ID = 2 has 3 credits and she is repeated 4 times
Tag: exists
sql server – checking existence for each row in insert
I need to do an insert and check for each row if the field “partita_iva” is already in this table, if yes the field “flag” must be 1, if not then must be 0. I did this, but it set 1 for all the rows, …
Scale CASE WHEN to retrieve non-holiday dates
I have table containing records with start and end dates, so I have to grab every record that started on a Friday, and if any Friday is a holiday, get Thursday, and if Friday and Thursday are holidays,…
Why should I use EXISTS() function in MySQL?
I have this query: And when I remove that EXISTS() function, still my code works: So why should I write that? What’s its advantage? Answer In short: EXISTS returns when it finds the first result instead of fetching all matching records (so it is more efficient when there are multiple records matching th…
Return 1 if number exists in table and 0 otherwise
I want to return 1 if some number already exists in table and 0 otherwise. I tried something but it doesn’t work: I want something similar to exists function that already exists in PostgreSQL, but instead of true and false I want 1 or 0. Answer EXISTS yields a boolean result. The simple way to achieve w…
How to update a table if values of the attributes are contained within another table?
I’ve got a database like this one: I’m trying to create a query that would enable me to update the value of the status attribute inside the incident table whenever the values of all of these three attributes: tabor_vatrogasci, tabor_policija, and tabor_hitna are contained inside the izvještaj_tabo…
Best way to test if a row exists in a MySQL table
I’m trying to find out if a row exists in a table. Using MySQL, is it better to do a query like this: SELECT COUNT(*) AS total FROM table1 WHERE … and check to see if the total is non-zero or is …