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 the criteria) EXISTS is semantically correct. When there
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 what you are asking
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_tabora table as a value of the oznaka_tabora attribute. If, for example, the values
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 …