Double Quotes vs. Single Quotes in PostgreSQL: When Should I Use Which?

Double quotes and single quotes in PostgreSQL

When using PostgreSQL, you may have encountered errors related to the usage of double quotes in queries. This article aims to clarify the difference between single quotes and double quotes in PostgreSQL and provide a comprehensive understanding of their usage and applications.

Double quotes: table and column identifiers

Double quotes (") are mainly used to enclose table and column identifiers in PostgreSQL. When you create a table or column whose name contains special characters or spaces, you need to use double quotes to enclose the identifiers of tables and columns. They are distinguished from regular keywords or identifiers. By surrounding an identifier in double quotes, you can explicitly indicate that it represents a table or column name

.

Example:

<code class="language-sql">CREATE TABLE "Employee" (
  "Employee_ID" INT PRIMARY KEY,
  "Employee_Name" VARCHAR(255)
);</code>

Single quotes: string constants

Single quotes (') are used to enclose string constants, such as text or dates, in PostgreSQL. String constants represent actual values ​​that can be stored in the column, rather than table or column names. String constants must be enclosed in single quotes to prevent them from being interpreted as identifiers.

Example:

<code class="language-sql">SELECT * FROM "Employee" WHERE "Employee_Name" = 'Elina';</code>

When to use double quotes and when to use single quotes

In summary, double quotes are used for table and column identifiers, while single quotes are used for string constants. This distinction is critical to avoid ambiguity and ensure that PostgreSQL queries execute correctly.

Note: While double quotes are not required for simple table or column names, it is recommended to use them consistently for the sake of code clarity and maintainability.

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