![]() Expressions COALESCE () returns the current value of the first expression that initially doesn’t evaluate to null. In this case, I set it to output (null) whenever a null value is returned. Left join (select id, date_trunc('seconds', min(time2)) as date2 from table1 where time2:date = now()::date group by id) q3 on q1.id = q3.idĪnd the matter is to replace those empty field above with any string I imagine. By default, the psql terminal outputs the empty string whenever a null value is returned. Left join (select id, date_trunc('seconds', max(time)) as date from table2 where time::date = now()::date group by id) q2 on q1.id = q2.id Sample query: select q1.id, q2.date, q3.date2 So I tried to use COALESCE function, but no result (I got error: invalid input syntax for timestamp: 'anystring': select column1, coalesce (datetrunc ('seconds. Those empty fields are placed in a 'timestamp without timezone' column. Coalesce will take a large number of arguments. Thus: SELECT COALESCE(null, null, 5) returns 5, while. Coalesce will return the first non null value in the list. So I tried to use COALESCE function, but no result (I got error: invalid input syntax for timestamp: "any_string": select column1, coalesce(date_trunc('seconds', min(date)), 'any_string') as column2 Those empty fields are placed in a "timestamp without timezone" column. If you need to support Postgres and Oracle from within the same code base, then you'll need to find a way to use different SQL depending on which database you connect to.I'm trying to replace some empty (NULL) fields, which I get as a result of my query, with any string I want. If this is a migration, then you only need to do it once. So you will have to bite the bullet and adjust your code. ![]() ![]() It stores the costs of each service a client gets in this format " KES 0.80". However in Oracle 'foo'||null yields 'foo' whereas in every other database that yields null - and there is no way you can make Postgres do that (unless you change Postgres' source code) I have a cost column in my postgres db whose type is varchar. In general all expressions involving NULL should yield NULL. Because Oracle also is non-standard when the concatenation operator || is involved (just the other way round: null is treated as ''). However, that will still not make Postgres behave like Oracle. If you really need this, you will have to convert empty strings to null when you save them (e.g. There is no configuration option that will make Postgres behave like Oracle here. It is a string with no characters, with a length of 0. A string literal of '' is a string whose value we know. A NULL value is a value that we don't know. Logically, for a DBMS, that would be wrong. The only database that treats an empty string like a NULL value, is Oracle. There is no need to use a SELECT statement to use a constant value.Įdit: it just occurred to me what you might mean with "config level". However, you can use is null or (less preferentially) coalesce (). I have tried making the second parameter numerous things (such as COALESCE(ARRAYAGG(tags.tag), ARRAY()), but they all result in syntax. I tried COALESCE(ARRAYAGG(tags.tag)) as tags but it still returns an array with null. Note that Oracle's behaviour is non-standard and no other DBMS treats '' the same as null in comparisons.ītw: your condition WHERE ( SELECT '' FROM dual) IS NULL could be simplified to WHERE '' IS NULL. The aggregate docs say 'The coalesce function can be used to substitute zero or an empty array for null when necessary'. Well, if you don't want to use the obvious and simple solution nullif(., '') is null then you need to check for both an empty string and null: where the_column is null or the_column = ''
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