![]() But still you have the power of doing that by providing a function that does the conversion in exactly the way you want to have it:Ĭreate or replace function f_convert_to_date ( pv_text in text ) returns date Psql: ERROR: invalid input syntax for type date: "First-January-19"Īs PostgreSQL has no idea how to do the conversion this will fail, no surprise here. Postgres=# insert into t1 values (3,'Third-January-19') Postgres=# insert into t1 values (2,'Second-January-19') Postgres=# insert into t1 values (1,'First-January-19') Postgres=# alter table t1 alter column b type date using (b::date) Postgres=# insert into t1 values (3,'0') Postgres=# insert into t1 values (2,'0') Postgres=# insert into t1 values (1,'0') +-+-+-+-įor our data in the “b” column that does work. ![]() Postgres=# alter table t1 alter column b type date using (b::date) Ĭolumn | Type | Collation | Nullable | Default But the “HINT” does already tell us what we might need to do: This does not work as PostgreSQL in this case can not know how to go from one data type to another. HINT: You might need to specify "USING b::date". Psql: ERROR: column "b" cannot be cast automatically to type date Postgres=# alter table t1 alter column b type date Let's try the most obvious way and let PostgreSQL decide what to do: What other options do we have to convert "b" to a real date without changing the name of the column. Is there a better way of doing that? Let’s start from scratch: Postgres=# update t1 set c = to_date('YYYYMMDD',b) īut what is the downside of that? This will probably break the application as the column name changed and there is no way to avoid that. Postgres=# alter table t1 add column c date Another option would be to add another column with the correct data type, populate that column and then drop the original one: Psql: ERROR: cannot use column reference in DEFAULT expression Postgres=# alter table t1 add column c date default (to_date('YYYYDDMM',b)) What options do we have to fix that? We could try something like this: ![]() For humans it seems obvious that the second column in reality contains a date but stored as text. What do we have here? A simple table with two columns: Column “a” is an integer and column “b” is of type text. Postgres=# create table t1 ( a int, b text ) PostgreSQL has a quite clever way of doing that.įrequent readers of our blog might know that already: We start with a simple, reproducible test setup: Depending on the current format of the data it might be easy to fix or it might become more complicated. But how many times did you see applications that store dates or numbers as text or dates as integers? This is not so uncommon as you might think and fixing that could be quite a challenge as you need to cast from one data type to another when you want to change the data type used for a specific column. You can do the same thing in a more compact way if you can concat the commas at the beginning and use substring to skip the first one so you don't need to do a sub-query: SELECT DISTINCT ST2.Usually you should use the data type that best fits the representation of your data in a relational database. ![]() LEFT(Main.Students,Len(Main.Students)-1) As "Students" I used the following T-SQL: SELECT Main.SubjectID, ![]() Result I expected was: SubjectID StudentName If there is a table called STUDENTS SubjectID StudentName In SQL 2005 I found that XML PATH method can handle the concatenation of the rows very easily. I had a similar issue when I was trying to join two tables with one-to-many relationships. If you are on SQL Server 2017 or Azure, see Mathieu Renda answer. This appliaction do not check database schema to use variables of specific type for each column, it simply uses strings, and in reality this PreparedStatement looks like: InsertSQL("INSERT INTO " + table_name + " (" + columns + ") VALUES (" + question_marks + ")", csv_data) I know that in PostgreSQL I can use: INSERT INTO test (intcol) VALUES (1.7) Īnd then PostgreSQL rounds it and inserts 2, but I want to know if I can do similar thing for strings.Īs of question "why?" I can answer that this is part of bigger apliaction which uses PreparedStatement where all parameters are strings. Oracle rounds it and inserts 2, while Informix truncates it and inserts 1. I have tried such code in Oracle and Informix. INSERT INTO test (intcol) VALUES ('1.7') Īnd fails with: ERROR: invalid input syntax for integer: "1.7" Such SQL looks like: INSERT INTO test (intcol) VALUES ('2') It works very well for strings with values such as 1, 10, etc., but fails for values with decimal dot: 3.14. Some table have integer column for which I want to insert string value with number. ![]()
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |