Using orchad 1.6 in the migration file I have just altered a table and added a column. I need this column to be NotNull, but it doesnt allow you to alter a table enter a NotNull type, so i've used Nullable and entered data into the existing columns.
I then want to edit this column and change it to a Nullable, but am unsure how....
public int UpdateFrom37()
{
SchemaBuilder.AlterTable("ManufacturedProductOrders", table => table
.AddColumn<DateTime>("DateOrdered", c => c.Nullable())
);
return 38;
}
public int UpdateFrom38()
{
SchemaBuilder.AlterTable("ManufacturedProductOrders", table => table
.AlterColumn("DateOrdered", c => c.WithType(dbType.???????????
);
}
I guess you want to change from NULL to NOT NULL, right? The code above clearly states that you already have a nullable column.
AlterColumn command does not currently allow changing column 'nullability'.
Your best option is to issue a manual ALTER TABLE command through SchemaBuilder.ExecuteSql() or directly in the database. You can read about it eg. here.
Related
I have a query (Update statement) wrapped in a function and will need to perform the same statement on multiple columns during the course of my script
async function update_percentage_value(value, id){
(async () => {
const client = await pool.connect();
try {
const res = await client.query('UPDATE fixtures SET column_1_percentage = ($1) WHERE id = ($2) RETURNING *', [value, id]);
} finally {
client.release();
}
})().catch(e => console.log(e.stack))
}
I then call this function
update_percentage_value(50, 2);
I have many columns to update at various points of my script, each one needs to be done at the time. I would like to be able to just call the one function, passing the column name, value and id.
My table looks like below
CREATE TABLE fixtures (
ID SERIAL PRIMARY KEY,
home_team VARCHAR,
away_team VARCHAR,
column_1_percentage INTEGER,
column_2_percentage INTEGER,
column_3_percentage INTEGER,
column_4_percentage INTEGER
);
Is it at all possible to do this?
I'm going to post the solution that was advised by Sehrope Sarkuni via the node-postgres GitHub repo. This helped me a lot and works for what I require:
No column names are identifiers and they can't be specified as parameters. They have to be included in the text of the SQL command.
It is possible but you have to build the SQL text with the column names. If you're going to dynamically build SQL you should make sure to escape the components using something like pg-format or use an ORM that handles this type of thing.
So something like:
const format = require('pg-format');
async function updateFixtures(id, column, value) {
const sql = format('UPDATE fixtures SET %I = $1 WHERE id = $2', column);
await pool.query(sql, [value, id]);
}
Also if you're doing multiple updates to the same row back-to-back then you're likely better off with a single UPDATE statement that modifies all the columns rather than separate statements as they'd be both slower and generate more WAL on the server.
To get the column names of the table, you can query the information_schema.columns table which stores the details of column structure of your table, this would help you in framing a dynamic query for updating a specific column based on a specific result.
You can get the column names of the table with the help of following query:
select column_name from information_schema.columns where table_name='fixtures' and table_schema='public';
The above query would give you the list of columns in the table.
Now to update each one for a specific purpose, You can store the result set of column name to a variable and pass that variable to the function to perform the required action.
I'd like to switch an actual system importing data into a PostgreSQL 9.5 database from CSV files to a more efficient system.
I'd like to use the COPY statement because of its good performance. The problem is that I need to have one field populated that is not in the CSV file.
Is there a way to have the COPY statement add a static field to all the rows inserted ?
The perfect solution would have looked like that :
COPY data(field1, field2, field3='Account-005')
FROM '/tmp/Account-005.csv'
WITH DELIMITER ',' CSV HEADER;
Do you know a way to have that field populated in every row ?
My server is running node.js so I'm open to any cost-efficient solution to complete the files using node before COPYing it.
Use a temp table to import into. This allows you to:
add/remove/update columns
add extra literal data
delete or ignore records (such as duplicates)
, before inserting the new records into the actual table.
-- target table
CREATE TABLE data
( id SERIAL PRIMARY KEY
, batch_name varchar NOT NULL
, remote_key varchar NOT NULL
, payload varchar
, UNIQUE (batch_name, remote_key)
-- or::
-- , UNIQUE (remote_key)
);
-- temp table
CREATE TEMP TABLE temp_data
( remote_key varchar -- PRIMARY KEY
, payload varchar
);
COPY temp_data(remote_key,payload)
FROM '/tmp/Account-005'
;
-- The actual insert
-- (you could also filter out or handle duplicates here)
INSERT INTO data(batch_name, remote_key, payload)
SELECT 'Account-005', t.remote_key, t.payload
FROM temp_data t
;
BTW It is possible to automate the above: put it into a function (or maybe a prepared statement), using the filename/literal as argument.
Set a default for the column:
alter table data
alter column field3 set default 'Account-005'
Do not mention it the the copy command:
COPY data(field1, field2) FROM...
I have a requirement on adding a date column to a table with default value is set by oracle's sysdate as follows
EXAMPLE {
...
CREATED_ON DATE DEFAULT SYSDATE
}
I want to use slick table ddl to create the table using
object ExampleTable extends Table[...]("EXAMPLE") {
def createdOn = column[java.sql.Date]("CREATED_ON", Default (?))
}
it seems there is no available sysdate for the default value, should I handle this default value programmatically or is there still a way using Slick?
Thanks,
I don't believe it's possible to use O.Default for your situation. When trying O.Default(new Date()), it would default the field to the date the ddl was executed, and not to sysdate.
I think the easiest workaround would be to use DBType to define the entire column, i.e.
def createdOn = column[java.sql.Date]("CREATED_ON", DBType("date default sysdate"))
You can verify this by inspecting the ExampleTable.ddl object.
I'm trying to add a new column to ProjectRecord table and i want to allow null values,
Code:
SchemaBuilder.AlterTable("ProjectRecord", table => table.AddColumn("Related", DbType.Int32));
Thanks.
Krbnr.
.AddColumn<int>("Related", c => c.Nullable())
An often use-case with Cassandra is storing the data in the column names of the dynamically created column family. In this situation the row values themselves are not needed, and a usual practice is to store nulls there.
However, when dealing with Hector, it seems like there is no way to insert null value, because Hector HColumnImpl does an explicit null-check in the column's constructor:
public HColumnImpl(N name, V value, long clock, Serializer<N> nameSerializer,
Serializer<V> valueSerializer) {
this(nameSerializer, valueSerializer);
notNull(name, "name is null");
notNull(value, "value is null");
this.column = new Column(nameSerializer.toByteBuffer(name));
this.column.setValue(valueSerializer.toByteBuffer(value));
this.column.setTimestamp(clock);
}
Are there any ways to insert nulls via Hector? If not, what is the best practice in the situation when you don't care about column values and need only their names?
Try using an empty byte[], i.e. new byte[0];