I am attempting to change a column name but there is an issue because my original column name has a number.
Here is what my table columns looks like
name price small medium large xl 2xl 3xl
When i do the following
ALTER TABLE tableName
RENAME small TO abc;
It executes well.
However when i do the following
ALTER TABLE tableName
RENAME 2xl TO xxl;
I get error saying syntax error at or near "2"
Does this mean i can never change this column's name because it starts with a numeric value?
Any time a column name begins with a non-alpha character, or contains special characters (spaces, etc) or is a keyword like "from," (but don't do that), you have to put the column name in quotes:
alter table tableName rename "2xl" to xxl;
As an aside, it's generally advisable to avoid object names that require double quotes. It's just more work in everything else. It's not wrong precisely speaking, just more work.
Enclose the identifier with the special characters in double quotes.
ALTER TABLE tablename
RENAME "2xl" TO xxl;
Related
I have a db table say, persons in Postgres handed down by another team that has a column name say, "first_Name". Now am trying to use PG commander to query this table on this column-name.
select * from persons where first_Name="xyz";
And it just returns
ERROR: column "first_Name" does not exist
Not sure if I am doing something silly or is there a workaround to this problem that I am missing?
Identifiers (including column names) that are not double-quoted are folded to lowercase in PostgreSQL. Column names that were created with double-quotes and thereby retained uppercase letters (and/or other syntax violations) have to be double-quoted for the rest of their life:
"first_Name"
Values (string literals / constants) are enclosed in single quotes:
'xyz'
So, yes, PostgreSQL column names are case-sensitive (when double-quoted):
SELECT * FROM persons WHERE "first_Name" = 'xyz';
Read the manual on identifiers here.
My standing advice is to use legal, lower-case names exclusively so double-quoting is never required.
To quote the documentation:
Key words and unquoted identifiers are case insensitive. Therefore:
UPDATE MY_TABLE SET A = 5;
can equivalently be written as:
uPDaTE my_TabLE SeT a = 5;
You could also write it using quoted identifiers:
UPDATE "my_table" SET "a" = 5;
Quoting an identifier makes it case-sensitive, whereas unquoted names are always folded to lower case (unlike the SQL standard where unquoted names are folded to upper case). For example, the identifiers FOO, foo, and "foo" are considered the same by PostgreSQL, but "Foo" and "FOO" are different from these three and each other.
If you want to write portable applications you are advised to always quote a particular name or never quote it.
The column names which are mixed case or uppercase have to be double quoted in PostgresQL. So best convention will be to follow all small case with underscore.
if use JPA I recommend change to lowercase schema, table and column names, you can use next intructions for help you:
select
psat.schemaname,
psat.relname,
pa.attname,
psat.relid
from
pg_catalog.pg_stat_all_tables psat,
pg_catalog.pg_attribute pa
where
psat.relid = pa.attrelid
change schema name:
ALTER SCHEMA "XXXXX" RENAME TO xxxxx;
change table names:
ALTER TABLE xxxxx."AAAAA" RENAME TO aaaaa;
change column names:
ALTER TABLE xxxxx.aaaaa RENAME COLUMN "CCCCC" TO ccccc;
You can try this example for table and column naming in capital letters. (postgresql)
//Sql;
create table "Test"
(
"ID" integer,
"NAME" varchar(255)
)
//C#
string sqlCommand = $#"create table ""TestTable"" (
""ID"" integer GENERATED BY DEFAULT AS IDENTITY primary key,
""ExampleProperty"" boolean,
""ColumnName"" varchar(255))";
I have a table that has a column, file_name. I added file names that contain underscores using insert. Upon select I see spaces where the underscores should be. Apparently the underscore is used for formatting and needs to be escaped.
What is the proper way to insert values with underscores?
How can I update the values with spaces by replacing all spaces with underscores?
What is the proper way to select a row using where when the value has an underscore, such as where file_name = "some_file.txt"
In other words, how and when does the underscore need to be escaped?
There is no need to escape underscores in string literals in Postgres. See this example. Your case may be caused by a strange behavior of client application. Test your queries in psql.
I'm trying to organize my PosgtresSql tables according to the application components they correspond to. For example, tables related to 'story' such as 'story_contents', 'story_comments', 'story_layout': would it best to keep a simple '' naming convention as presented? Would there be any drawback to using a '.' instead of ''? ... or is there a best practice that I'm completely overlooking?
Short answer:
Sure, if you place the entire database/table/column name reference in quotes
Long answer:
In Postgres, and most other databases, the dot is used to separate database name from table name, and table name from column name. For example, if you had a database called MyDB, with a table called MyTable and column in that table MyCol, then you could write the following SELECT statement:
SELECT MyDB.MyTable.MyCol
FROM MyDB.MyTable
However, if your database, table, and/or column names themselves had dots in them, then doing a SELECT might not work. In this case, I believe you can escape the fully qualified name (or portion) with quotes. So, if you had a column called MyCol.Col1, you could do the following:
SELECT "MyDB.MyTable.MyCol.Col1"
FROM MyDB.MyTable
The comment by #vector seems to be pointing in the right direction (no pun intended), and you should lean towards using underscores or some other character to separate out your schema names, rather than using a dot.
I'm programatically adding data to a PostgreSQL table using Python and psycopg - this is working fine.
Occasionally though, a text value is too long for the containing column, so I get the message:
ERROR: value too long for type character varying(1000)
where the number is the width of the offending column.
Is there a way to determine which column has caused the error? (Aside from comparing each column's length to see whether it is 1000)
Many thanks to #Tometzky, whose comment pointed me in the right direction.
Rather than trying to determine which column caused the problem after the fact, I modified my Python script to ensure that the value was truncated before inserting into the database.
access the table's schema using select column_name, data_type, character_maximum_length from information_schema.columns where table_name='test'
when building the INSERT statement, use the schema definition to identify character fields and truncate if necessary
I don't think there's an easy way.
I tried to set VERBOSITY in psql, as I assumed this would help, but unfortunately not (on 9.4):
psql
\set VERBOSITY verbose
dbname=> create temporary table test (t varchar(5));
CREATE TABLE
dbname=> insert into test values ('123456');
ERROR: 22001: value too long for type character varying(5)
LOCATION: varchar, varchar.c:623
This might be something that warrants discussion on the mailing list, as you are not the only one with this problem.
SQL Query on PostgreSQL:
insert into TOKEPOOLAMT (TOKEPOOLAMT.TOKEPOOLAMTID,TOKEPOOLAMT.TOKERULEID)
values (151, 176);
Giving error:
com.edb.util.PSQLException:
ERROR: column "tokepoolamt" of relation "tokepoolamt" does not exist
But:
insert into TOKEPOOLAMT (TOKEPOOLAMTID,TOKERULEID) values (151, 176);
is working fine.
Can anybody explain why alias name with column in insert statement not working?
There are no aliases involved here. Your error is that column names in the column list of an INSERT command cannot be table-qualified. #pozs already provided the fitting quote from the manual in his comment.
I don't think it's an issue of case. I tried with both the cases.
That's missing the point. In Postgres, identifiers are folded to lower case unless double-quoted. If you double-quoted a name at creation time you preserved a case sensitive spelling and need to double-quote for the rest of the object's life - unless it was a legal, lower-case name to begin with, then quoting won't make a difference. Details:
Are PostgreSQL column names case-sensitive?