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Tag: unique

Generating never used before random number in SQL

I am using the function below to generate a random number between 0 and 99999999999. However, I need to make sure that the returned number has never been used before in the same app. In .net I would create a while loop and keep looping until the returned value is not found in a table that stores previously used values.

non UNIQUE constraints

So, I got in this situation: I create a table (let say model_a), in this table I have 2 cols (let say col1 and col2). I need a constraint that satisfy this reality: It’s not UNIQUE constraint, you can duplicate the first row. The only one time this constraint active is col1 is the same but col2 is different. Need

PostgreSQL Partial Indexes and UPSERT

After googling a lot my question is described below: Attempting to insert values: Results in: Altho this works(per spec): PostgreSQL documentation stands that it should work PostgreSQL v9.5 My aim is to find way to create unique index on this table on multiple nullable columns and update old rows with new ones on UPSERT Answer The conflict_target used in on


I have a table for storing coupons/discounts, and I want to use the coupon_code column as the primary key, which is a VARCHAR. My rationale is that, each coupon will have a unique code, and the only commands I will be running are SELECT … FROM … WHERE coupon_code=’..’ I won’t be doing any joins or indexing, and I don’t

Get number of values that only appear once in a column

Firstly, if it is relevant, I’m using MySQL, though I assume a solution would work across DB products. My problem is thus: I have a simple table with a single column. There are no constraints on the column. Within this column there is some simple data, e.g. I need to get the number/count of values that only appear once. From