If you’re getting an error that reads something like “Column names in each table must be unique. Column name ‘c1’ in table ‘t1’ is specified more than once” in SQL Server, it appears that you’re trying to create a table with duplicate column names, or you’re trying to add a column to a table that already has a column of that name.
Column names must be unique within each table.
Continue readingIn SQL, we can use the CREATE TABLE IF NOT EXISTS statement to create a table only if it doesn’t exist. The benefit of doing this is that we won’t get an error if there’s already a table with the same name.
But SQL Server doesn’t support this syntax – at least not in the current version of SQL Server at the time of writing (SQL Server 2022) .
So with SQL Server, we need to do a bit of extra work.
Continue readingMany RDBMSs implement IF EXISTS and IF NOT EXISTS syntax modifiers that can be used with DDL object creation, modification, and deletion, such as CREATE TABLE and DROP TABLE statements, to name just a couple.
These syntax modifiers allow us to run such statements without getting an error in the event that the object already exists (if we’re trying to create it or modify it) or doesn’t exist (if we’re trying to drop it).
Continue readingIn MySQL, we can use the SHOW CREATE TABLE statement to generate a CREATE TABLE script for existing tables. This enables us to recreate the table without having to manually type out the table’s definition.
When creating a table with SQL, we can specify that the table is only to be created if it doesn’t already exist. Doing this prevents any errors from occurring in the event that the table already exists.
Here are some examples of doing this in various RDBMSs.
Continue readingWe can use MariaDB’s SHOW CREATE TABLE statement to generate a CREATE TABLE script for existing tables in the database. This allows us to recreate the table without having to manually type out the table’s definition.
The statement requires SELECT privilege for the table.
Probably the most common way of creating a table in SQL is to use a basic CREATE TABLE statement, along with the table’s definition. But that’s not the only way of doing it.
Below are five options for creating a table when using SQL.
Continue readingThe very useful CREATE TABLE IF NOT EXISTS syntax was finally introduced in Oracle Database – Oracle Database 23c to be precise. This syntax allows us to run a CREATE TABLE statement without getting an error if the table already exists.
Earlier versions of Oracle don’t support the IF NOT EXISTS clause, and so if we want to avoid any nasty errors resulting from trying to create a table that already exists, we need to do a bit of extra work.
Dropping a table in SQL easy. You simply use DROP TABLE myTable where myTable is the name of the table you want to drop. You can use this method to drop a table in SQL Server via T-SQL script.
But you’ll get an error if the table doesn’t actually exist. That is, unless you check for the existence of the table first.
Below are four ways of using T-SQL to check whether the table exists before dropping it.
Continue readingIn SQLite, you can use the IF NOT EXISTS clause of the CREATE TABLE statement to check whether or not a table or view of the same name already exists in the database before creating it.
Creating a table without this clause would normally result in an error if a table of the same name already existed in the database. But when using the IF NOT EXISTS clause, the statement has no effect if a table already exists with the same name.