Value-based filtering
Restrict a select, update, or delete query to rows matching a supplied value.
Drizzle ORM · Function
eq
eq creates an equality filter for a value or another column. Use it in query conditions such as where and joins.
How it works
eq builds an equality condition for a column or SQL expression and a value or another column. Pass the resulting condition to query methods such as where or join methods such as leftJoin; Drizzle translates it to SQL equality syntax and parameterizes supplied values.
Syntax
eq(left, right)Parameters
| Name | Type | Description |
|---|---|---|
left | SQL expression | Column or SQL expression on the left side of the equality comparison. |
right | value or SQL expression | Value or column/SQL expression compared with the first operand. |
Returns
An SQL condition representing equality between the two operands.
Key points
eqrepresents the equality comparison between its first expression and the supplied second operand.- Import
eqfrom the maindrizzle-ormpackage alongside the other filter and conditional operators. - Use the predicate directly inside a query's
whereclause to retain a concise, type-safe filter expression. - For a literal comparison, Drizzle generates SQL using the equality operator between the qualified column and the value.
- The second operand may be another column expression, enabling column-to-column equality checks.
- Column comparisons compile to SQL that places both qualified columns around the equality operator.
Common mistakes
- Values passed to
eqare parameterized automatically, so do not construct SQL by interpolating them yourself.
Example: Filter rows with equality
import { eq } from "drizzle-orm";
import { users } from "./schema";
const result = await db
.select()
.from(users)
.where(eq(users.id, 42));Selects the user whose id equals 42.
When to use it
Join predicates
Join related tables by requiring two key columns to match.
Expression comparison
Find rows where two columns or SQL expressions have equal results.
Interview questions
QWhat does eq do?
eq creates an equality predicate. For example, eq(table.column, 5) becomes a condition equivalent to table.column = 5, and it can be supplied to where.
Follow-up: How can it compare columns instead of a literal? Pass the second column expression, such as eq(table.column1, table.column2); Drizzle emits column-to-column equality.
QHow is eq commonly used in a select query?
Import eq from drizzle-orm and pass it to a query condition method. A typical usage is .where(eq(users.id, 42)).
Follow-up: Can it be used in joins? Yes. The documentation demonstrates it as the join condition in .leftJoin(users, eq(posts.ownerId, users.id)).
QCan eq compare two columns?
The operator supports comparing a table column with another table column, not only with a literal. The documentation shows eq(table.column1, table.column2) producing equality between those two columns.
Follow-up: What SQL shape does a literal comparison produce? It produces a parameterized equality predicate, such as users.id = $1, with the value supplied separately.
Related
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