In PostgreSQL, the constraints are used to apply some rules on the table’s column. In Postgres, theNOT NULLconstraint prevents NULL entries from being inserted into a column. In simple terms, the table columns declared with aNOT NULLconstraint take only non-null entries. In Postgres, theNOT...
Use the below-provided syntax to add/set a UNIQUE constraint on various columns of an existing PostgreSQL table: ALTERTABLEname_of_tableADDCONSTRAINTconstraint_nameUNIQUE(col_name_1, col_name_2, …); Here, in the above-stated syntax: -“name_of_table” indicates an existing ...
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UNIQUE:The UNIQUE constraint does not allow duplicate values to be inserted in the column CHECK: This constraint checks the value being inserted in a table. The check constraint has expressions that evaluate against the data being inserted. If the condition evaluates TRUE, the data will be insert...
Today, in PostgreSQL, we will be learning how to use UTC current time as the default time in our tables in PostgreSQL. UTC stands for COORDINATED UNIVERSAL TIME. It is the UNIVERSAL method of regulating clocks and time worldwide. Local Time Zones have time specified only for a certain locat...
PostgreSQL: The PostgreSQL clientpsqlhas a number of options you can use to reveal information about a given table. The\doption returns metadata of the named table: \dtable_name Copy Managing Constraints In MySQL, you can add constraints to existing tables as well as delete them withALTER TAB...
sudo apt-get install postgresql postgresql-contrib After installation, create a new user to manage the database we'll be creating: sudo adduserpostgres_user Log into the default PostgreSQL user (called "postgres") to create a database and assign it to the new user: ...
This article will introduce theINSERT ON DUPLICATE UPDATEin PostgreSQL. What doesINSERT ON DUPLICATE UPDATEmean? And why is it used? ADVERTISEMENT Whenever youINSERTrecords into a table, you add a data set with a uniquePRIMARY KEY. It could be an ID or an auto-generated number that is diffe...
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ADD CONSTRAINT actor_pkey PRIMARY KEY (actor_id); -- -- Name: idx_actor_last_name; Type: INDEX; Schema: public; Owner: postgres -- CREATE INDEX idx_actor_last_name ON public.actor USING btree (last_name); -- -- Name: actor last_updated; Type: TRIGGER; Schema: public; Owner: pos...