Add column if not exists postgres

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Add column if not exists postgres

Postgres add multiple column if not exists. Postgresql add column if not exists syntax error. Add column if not exists postgres 9.4. Add column if not exists postgres 9.5. Postgres 9.5 alter table add column if not exists. Postgresql 9.3 add column if not exists. Postgres 9.2 add column if not exists. Postgresql add column if not exists default value.

Sometimes, you need to write a SQL script that runs on multiple scripts should not fail. To address this need, in general you have the following options A 1. You can perform conditional SQL statements (with a little 'control) for example ? DROP TABLE IF EXISTS CASCADE; INSERT INTO (, ) SELECT 'pk_column_value', 'column_2_value' WHERE NOT EXISTS (SELECT 'Y' FROM where = 'some value'); 2. You can use the options provided in the database, for example by a CREATE OR REPLACE FUNCTION We had a similar requirement. We wanted to create a script that would update our data model from version to version x x + 1 and should not fail even if the script is run multiple time. We could not use any option above in the case of adding a column to an existing table. PostgreSQL provides an option to check if the column already exists or not while dropping the column. However, it does not provide straight forward way while adding a column to check whether the column is already present in the table or not. In addition, we did not want to delete the column and then add ? column because in that case we might lose your data (if there is some). Solution to the problem is to query the tables where Postgres stores the metadata schema. To check if a column exists or not in a particular table, it is necessary to perform a SELECT query on the join of two tables A and PG_ATTRIBUTE pg_class, which stores information about, respectively, columns and tables (query is highlighed code given below). CREATE OR REPLACE FUNCTION test.upgrade_schema () returns void AS $ BODY $ DECLARE var_column_exists VARCHAR (32); BEGIN SELECT INTO A.ATTNAME VAR_COLUMN_EXISTS DA PG_ATTRIBUTE A, C pg_class WHERE A.ATTRELID C.OID = E = A.ATTNAME 'column_to_add' E = C.RELNAME 'table_to_alter'; SE var_column_exists IS NULL THEN ALTER TABLE ADD COLUMN test.table_to_alter column_to_add varchar (256) Default NULL; END IF; END; $ BODY $ LANGUAGE plpgsql; References http: //postgresql .org / docs / 8.1 / static / catalog-pgattribute.html INFORMATION_SCHEMA.COLUMNS You can use to check if the column exists or not. CREATE TABLE t (RID int, int foo); t INSERT VALUES (1,1), (2,2), (3,3); CREATE FUNCTION FNN (id int, int new_val) returns void AS $$ BEGIN IF NOT EXISTS (SELECT 1 FROM WHERE INFORMATION_SCHEMA.COLUMNS TABLE_NAME = 't' AND COLUMN_NAME = 'bar') THEN ALTER TABLE t ADD int bar; END IF; UPDATE t SET = new_val bars WHERE id = free; END; $$ LANGUAGE plpgsql; FNN SELECT (1, 15); SELECT * FROM t; free | Foo |. bar -: | -: | ---: 2 | 2 |. null 3 | 3 | null 1 | 1 | 15 db here m IA using Python to write in a Postgres database: sql_string = "INSERT INTO cent (name_slug, state) VALORI (" sql_string + = hundred +", '+ hundred_slug +', "+ status + ");"But since some of my lines are identical, I get the following error: psychopg2.Integrityerror: the duplicate key value violates the unique constraint ?hundred_pkey? How can I write a command ? ?Insert? if this line does not exist already? I have seen complex instructions like this recommended: if exists (select * from invoices where invoicesid = ? TM 12 345 ') update invoices invoices set invoices set = ? TM True' where invoiceid = ? TM 12 345 'else insert into invoices (invoiceid, turnover) values (? TM 12 345 ', ? TM TR EU') End if but first of all, it is this overkill for what I need, and secondly, how can I do one like a simple string? How can I write a SQL ? ?Insert? education if this line does not already exist? There is a nice way to make conditional insert in PostgreSQL: Insert Into Example_Table (ID, Name) Select 1, ? TM John 'Where Not Esists (Select ID from example_table where id = 1); Caveat This approach is not 100% reliable for simultaneous writing operations. There is a very small race condition between the select in the anti-semi-joint not exists and the same insert. In these conditions it can fail. Postgres 9.5 (released starting from 07.01.2016) offers a command ?Upsert?: Insert ... on Conflict Nothing / Update solves many of the thin problems that you can meet when using the competitor operation, which some other answers They propose. An approach could be to create a non-bound (unique indexes) table to enter all your data and make a selection from that to make your insertion in your hundreds table. It would be really high. I suppose all three columns are distinguished in my example, so for Step3 the NOT EXITS JOIN changes to join only on the individual columns in the hundreds table. Create a temporary table. See the doctors here. Create Temporary Table Temp_Data (name, name_slug, status); Insert the data in the Temp table. INSERT INTO TEMP_DATA (name ,_name_lug, status); Adds any indexes to the Temp table. Make the main table insert. Inserted in one hundred (name, name_slug, status) Select Distinct Name, name_slug, status from one hundred where you do not exist (select ? TM x 'from temp_data where temp_data.name = cent.name and temp_data.name_slug = cent.name_slug and temp_data. status = status); Unfortunately, PostgreSQL does not support N? ? Merge N? ? Duplicate Key Update, so you will need to do so in two instructions: invoices update invoices set = ? TM True 'where invoices = ? TM 12 345' Insert Into invoices (invoice, bills) Select ? TM 12 345 ', ? TM TRUE' WHERE ? TM 12 345 'NON IN (Select INVOCED FROM INVOICES) You can insert it into a function: Create or ROSPIACE FUNCTION FN_UPD_INVOICES (ID VARCHAR (32), Varchar invoices ( 32)) Restorna void as $$ Update Invoices Septure Septure = $ 2 WHERE invoices = $ 1; Insert Into invoices (invoice) Select $ 1, $ 2 WHERE $ 1 NOT IN (SELECT INVOCED FROM INFORMATION); $$ ? TM sql '; and just call it: select fn_upd_invoices (? TM 12 345 ', ? TM True') if you only want to insert or do not insert (and not update otherwise), you can do this this way (using the example of the bill): insert Into invoices (InviceD, (InviceD, SELECT '12 345', 'TRUE' WHERE NON ESISTS (SELECT 1 DA invoices WHERE invoiced = '12 345') You can use the VALORI' available in Postgres: INSERT INTO person (name) SELECT name DA person UNION VALUES ('Bob') EXCEPT SELECT name FR I know this question was a while ago, but I thought it might help someone. I think the easiest way to do that is through a trigger. For example: Create Function ignore_dups () Returns Trigger as $$ Start if it exists (Select * From hundreds h Where -- Assuming that all three fields are primary key h.name = NEW.name E h.hundred_slug = NEW.hundred_slug E h.status = NEW.status) Then returns NULL; Fine If; Return NEW; End; $$ Language plpgsql; Create Trigger ignore_dups before entering Hundreds for each row Run the procedure ignore_dups (); Run this code from a psql prompt (or how you like to query directly in the database). Then you can insert it as normal by Python. For example: sql = ?Insert In hundreds (name, name_slug, status) Values (%s, %s, %s) ? cursor.execute (sql, (hundred,undred_slug, status) Note that, like @Thomas_Wouters already mentioned, the code above takes advantage of the parameters rather than concatenate the string. INSERT .. Where NOT ESISTE is a good approach. And the conditions of competition can be avoided with the transaction "involution": BEGIN; LOCK TABLE 100 IN SHARE ROW EXCLUSIVE MODE; INSERT ...; COMMIT; The approach with the largest number of upvotes (from John Doe) somehow works for me but in my case from the 422 lines expected only 180. I couldn't find anything wrong and there are no mistakes, so I looked for a different simple approach. Using IF NOT FOUND THEN after a SELECT works perfectly for me. (described in PostgreSQL Documentation) Example from documentation: SELECT * INTO myrec FROM emp WHERE empname = myname; SE NOT FOUND THEN RAISE EXCEPTION 'empyee % not found', myname; END IF; psycopgs cursor class has the attribute rowcount. This read-only attribute specifies the number of rows that the last execution* () generated (for DQL instructions as SELECT) or which were affected (for DML instructions such as UPDATE or INSERT). In PostgreSQL, the ALTER TABLE instruction can be used to add, delete or change your table. If you want to add a column to a table, simply specify the ADD COLUMN clause in the ALTER TABLE statement. However, you will experience a mistake if you try to add an existing column. It is easy to avoid this error using the IF NOT EXISTS option with the ADD COLUMN clause. This option tells PostgreSQL to add the new column only if the column name does not exist in the table. In this article, we will take a closer look at the Postgres ADD COLUMN IF NOT EXISTS command and take a look at some examples of its use. Prerequisites To get the most out of this tutorial,make sure there are a couple of prerequisites: PostgreSQL must be installed on your computer so you can test our examples of the Postgres ADD COLUMN SE NOT EXISTS command. You... You... have some basic knowledge of PostgreSQL in order to follow with the instructions provided in this article. The Postgres IF NON EXISTS syntax Let's start with a quick look at the syntax for the IF NOT EXISTS option in a statement TABLE ALTER: TABLE OF ALTER NAME ADD COLUMN IF NOT EXISTs column_name [DATA TYPE] Let's talk about this syntax in a little bit more of a First, we specify the name of the table to which we want to add a column. We provide the IF NOT EXISTS option after the ADD COLUMN clause, and then specify the column name and its data type. The IF NOT EXISTS option will check if the specified column name exists in the table. With this option in place, no errors will be returned if you try to add a column that already exists. Postgres IF NO EXIST Example Before proceeding, let's create a sample table to use in our examples: CREATE TABLE employees (id SERIAL PRIMARY KEY, name VARCHAR (50), POSITION VARCHAR (50) ); The table called employees is now created. Add Column Now, let's add a new column to our table with the same name as an existing column. We will use the following statement ALTER TABLE: ALTER employees TABLE ADD COLUMN name VARCHAR (50); ERROR: COLUMN "employees" relationship name already EXIST This statement will return an error because the column "name" in the employee table already exists. To avoid this error, we can only use the IF NOT EXISTS option. Let's see what our statement looks like with this option: ALTER TABLE employees ADD COLUMN IF NOT EXISTS name VARCHAR (50); NOTE: COLUMN "name" of the "employees" report already EXISTS, skipping ALTER TABLE NOTE: The above statement did not return an error, but showed a message warning you that a column with the same name already exists. What do you think will happen if you try to add a column with the same name as an existing column but a different data type? Let's try and see: ALTER TABLE employees ADD COLUMN IF NOT EXISTS name TEXT; NOTE: COLUMN "name" of relation "employees" already EXISTS, skipping ALTER TABLE The column will not be added yet because a column with the same name already exists. Conclusion When you need to make a change to one of your PostgreSQL tables, it is easy to add, delete, or rename a column using the ALTER TABLE statement; however, an error may occur if you try to add a column that already exists. To make any errors, you can use the IF ALREADY EXISTS option after the ADD COLUMN clause in the TABLE declaration. In this article, we discussed the Postgres ADD COLUMN IF ALREADY EXISTS statement and reviewed some examples of how to use it. With our examples and step-by-step instructions, you will be able to add columns to a table without encountering errors in your PostgreSQL database.

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