#Postgresql insert into from select how to
#Postgresql insert into from select update

Privileges are tested once at statement start and are checked whether or not particular WHEN clauses are executed. If you specify an delete action, you must have the DELETE privilege on the target_table_name.

If you specify an insert action, you must have the INSERT privilege on the target_table_name.

#Postgresql insert into from select update

If you specify an update action, you must have the UPDATE privilege on the column(s) of the target_table_name that are referred to in the SET clause. Since actions are evaluated in their specified order, DO NOTHING can be handy to skip non-interesting source rows before more fine-grained handling. When DO NOTHING is specified, the source row is skipped. All actions refer to the target_table_name, though modifications to other tables may be made using triggers. The syntax of those commands is different, notably that there is no WHERE clause and no table name is specified. MERGE actions have the same effect as regular UPDATE, INSERT, or DELETE commands of the same names. No more than one WHEN clause is executed for any candidate change row. For each candidate change row, the first clause to evaluate as true is executed. For each candidate change row, the status of MATCHED or NOT MATCHED is set just once, after which WHEN clauses are evaluated in the order specified. MERGE provides a single SQL statement that can conditionally INSERT, UPDATE or DELETE rows, a task that would otherwise require multiple procedural language statements.įirst, the MERGE command performs a join from data_source to target_table_name producing zero or more candidate change rows. MERGE performs actions that modify rows in the target_table_name, using the data_source. Don’t forget that you can select fixed values if no column from the query has the info ( INSERT INTO X(p,c,age) SELECT personname, cityname, 23 FROM. The number of columns inserted to must match the number of columns selected. However, I trust that the general pattern shown first will suffice for your learning write a SELECT that shows the data you want to insert, then simply write INSERT INTO table(columns) above it. If you just want to mix every person with every city you can do: INSERT INTO employee(personname,cityname)īut be warned, two people and two cities will cause 4 rows to be inserted, and so on (20 people and 40 cities, 800 rows. Provide eg a cityname in Person (because it seems more likely that one city has many person) then you can do INSERT INTO employee(personname,cityname)īut even then, the tables are related between themselves and don’t need the third table so it’s perhaps something of an academic exercise only, not something you’d do in the real world In your case there isn’t really anything to join on because your one-column tables have no column in common. The general pattern for turning a select that has two base tables giving info, into an insert is: INSERT INTO table(column,list,here)

There doesn’t appear to be any obvious relationship between city and person which will make your life hard

#Postgresql insert into from select how to

The textbook I have for class doesn't dive into sub-queries like this and I can't find any examples similar enough to mine such that I can understand how to adapt them for this use case. Notice in the last block of code, where I'm doing an INSERT into the employee table, I don't know how to string together multiple SELECT sub-queries to get both the existing records from the person and city table such that I can create a new employee entry with attributes as such: create employee entry referencing existing records Create a employee table w/ForeignKey referenceĮname VARCHAR(255) REFERENCES person(pname) NOT NULL,Įcity VARCHAR(255) REFERENCES city(cname) NOT NULL, Create a city table + insert single row I am learning SQL (postgres) and am trying to insert a record into a table that references records from two other tables, as foreign keys.īelow is the syntax I am using for creating the tables and records: - Create a person table + insert single row