![]() I'd rather avoid a temporary table, if possible. Constraints can be defined on a single column or on multiple columns in the same table. ![]() )īecause there is no primary key for the row. ![]() I'm thinking a delete statement would be the best, but I can't simply write delete from table where row_id not in (select row_id. Viewed 5k times 2 I have a table in which I need unique EmpId. (WTF didn't we have a unique constraint from the start? Go figure.) How to add unique constraint in postgres on two columns where value of one column is true Ask Question Asked 5 years, 4 months ago. Specifically, the unique key would be over the columns. I'm trying to run a query equivalent to this: CREATE TABLE scores (id INT PRIMARY KEY NOT NULL, oppId INT NOT NULL, oppType TEXT NOT NULL, tree TEXT NOT NULL, version INT NOT NULL, score JSON NOT NULL, CONSTRAINT uniqscores UNIQUE(oppId, oppType, tree, version)). Normally we would do a delete command with a select distinct thrown in, but we don't have any distinguishing key for the rows. CREATE UNIQUE INDEX abcnullidx ON mytable (idA, idB) WHERE idC IS NULL This way you can enter for (idA, idB, idC) in your table: (1, 2, 1) (1, 2, 2) (1, 2, NULL) But none of these a second time. So, in this example, we would need to remove that second row before we could safely add the unique constraint. Specifically, the unique key would be over the columns iid, term. To create a unique index on a hypertable: Determine your partitioning columns. Here is the how to add a unique constraint to your table in PostgreSQL 9. In PostgreSQL, a primary key is a unique index with a NOT NULL constraint. The SQL tab displays the SQL code generated by dialog selections. The Unique constraint dialog organizes the development of a unique constraint through the following dialog tabs: General and Definition. If we add two different null values into a column in different. Unique constraints ensure that the data contained in a column, or a group of columns, is unique among all the rows in the table. Normally we would do a delete command with a select distinct thrown in, but we don't have any distinguishing key for the rows. But if you have non-unique entries in your table, it will fail. When we are using the unique constraint, an index on one or more columns generate automatically. The unique constraint spans two columns, and there is no primary key. So, in this example, we would need to remove that second row before we could safely add the unique constraint. (I'm certainly open to other syntax choices for resolving the ambiguity.We're trying to add a unique constraint to our postgres table in a way that deletes the duplicates rather than throwing an error. ON CONFLICT WITH CONSTRAINT constraint-name DO UPDATE SET count = count + 1 ON CONFLICT WITH INDEX idx DO UPDATE SET count = count + 1 This could be resolved with a little extra syntax: So far, the only issue with this proposal that I have been able to identify is that the name idx might be ambiguous if one of the columns were also named idx. ON CONFLICT (idx) DO UPDATE SET count = count + 1 In terms of restrictions, this is equivalent to a UNIQUE NOT NULL constraint however, a table may only have one primary key, whereas multiple columns can be constrained as. The upsert caluse could be changed to something like In PostgreSQL, a primary key constraint indicates that a particular column (or group of columns) in a database table can be used to identify a unique row in that table. Given that UNIQUE constraints CAN be named using the CONSTRAINT keyword and given that UNIQUE indexes are always named, it seems to me that it would be nice if the ON CONFLICT portion of "upsert-clause" could reference a constraint or index by name instead of replicating the "indexed-column" list as the "column-name-list" of the "upsert-clause".ĬREATE Table TBL (a, b, c, d, e, f, g, h, count INTEGER DEFAULT 1) CREATE UNIQUE INDEX idx on TBL tbl (a, b, c, d, e, f, g, h) INSERT INTO tbl (a, b, c, d, e, f, g, h) VALUES (.) ON CONFLICT (a, b, c, d, e, f, g, h) DO UPDATE SET count = count + 1 Therefore, if a unique index consists of a single column, only one null value is allowed-more than one null value would violate the unique constraint. Similarly, the "indexed-column" list in UNIQUE indexes can be pretty long. Sometimes the "indexed-column" list in UNIQUE constraints can be pretty long.
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