Each container in docker by default gets its own hostname and IP. When compose spins up the containers for you, it also places all of the containers on a network by default to permit DNS based discovery. What this means is that your database is not reachable on localhost, but you can reach it by … Read more
You need to add the PostgreSQL JDBC Driver in your project as mentioned in search.maven.org. Gradle: implementation ‘org.postgresql:postgresql:42.2.10’ Maven: <dependency> <groupId>org.postgresql</groupId> <artifactId>postgresql</artifactId> <version>42.2.10</version> </dependency> You can also download the JAR and import to your project manually. NOTE: Compile as used in this answer is deprecated. Replace with implementation as per 3.
Effectively, WHERE conditions and JOIN conditions for [INNER] JOIN are 100 % equivalent in PostgreSQL. (It’s good practice to use explicit JOIN conditions to make queries easier to read and maintain, though). The same is not true for a LEFT JOIN combined with a WHERE condition on a table to the right of the join. … Read more
Since Postgres 9.6, it is possible to specify a collation which will sort columns with numbers naturally. https://www.postgresql.org/docs/10/collation.html — First create a collation with numeric sorting CREATE COLLATION numeric (provider = icu, locale=”en@colNumeric=yes”); — Alter table to use the collation ALTER TABLE “employees” ALTER COLUMN “em_code” type TEXT COLLATE numeric; Now just query as you … Read more
Use a RECURSIVE CTE in Postgres: WITH RECURSIVE cte AS ( SELECT key, value, 1 AS level FROM taxonomy WHERE key = 0 UNION ALL SELECT t.key, t.value, c.level + 1 FROM cte c JOIN taxonomy t ON t.taxHier = c.key ) SELECT value FROM cte ORDER BY level; Details and links to documentation in … Read more
Download the PostgreSQL JDBC Driver from https://jdbc.postgresql.org/download/ Then replace the database configuration values by yours. from pyspark.sql import SparkSession spark = SparkSession \ .builder \ .appName(“Python Spark SQL basic example”) \ .config(“spark.jars”, “/path_to_postgresDriver/postgresql-42.2.5.jar”) \ .getOrCreate() df = spark.read \ .format(“jdbc”) \ .option(“url”, “jdbc:postgresql://localhost:5432/databasename”) \ .option(“dbtable”, “tablename”) \ .option(“user”, “username”) \ .option(“password”, “password”) \ .option(“driver”, “org.postgresql.Driver”) … Read more
The same effect can be replicated in Oracle either by using the first_value() function or by using one of the rank() or row_number() functions. Both variants also work in Postgres. first_value() select distinct col1, first_value(col2) over (partition by col1 order by col2 asc) from tmp first_value gives the first value for the partition, but repeats … Read more
This is what I do in PostgreSQL 9.2, although I must admit I did not find this approach documented. There is a function pg_trigger_depth() documented here, which I use to differentiate between original and nested calls in the trigger. CREATE TRIGGER trg_taxonomic_positions AFTER INSERT OR UPDATE OF taxonomic_position ON taxon_concepts FOR EACH ROW WHEN (pg_trigger_depth() … Read more
Like @a_horse commented, you would have to use the regular expression operator ~ to use bracket expressions. But there’s more. I suggest: SELECT * FROM tbl WHERE value ~ ‘^00[^0]’ ^ … match at start of string (your original expression could match at any position). [^0] … a bracket expression (character class) matching any character … Read more
The permissions article mentioned in the answer by Houari and Flimzy is a good reference material, but a direct answer (the quick fix I used) is: Right click the folder containing the data file(s) that permission was denied to and then click Properties. In the Folder’s Properties window, select the Security tab. Click the Edit … Read more