WHERE with LIKE pattern matching in SQL - Step-by-Step Execution

Concept Flow - WHERE with LIKE pattern matching

Start Query

↓

Apply WHERE clause

↓

Check LIKE pattern match

↓

Include row

↓

Return filtered rows

↓

End

The query starts, applies the WHERE clause, checks each row against the LIKE pattern, includes matching rows, excludes others, then returns the filtered result.

Execution Sample

SQL

SELECT name FROM employees
WHERE name LIKE 'A%';

This query selects employee names starting with 'A'.

Execution Table

Step	Row Data (name)	LIKE Pattern	Match Result	Action
1	Alice	'A%'	Yes	Include row
2	Bob	'A%'	No	Exclude row
3	Amanda	'A%'	Yes	Include row
4	Charlie	'A%'	No	Exclude row
5	Albert	'A%'	Yes	Include row
6	David	'A%'	No	Exclude row
Exit	-	-	-	All rows checked, query ends

💡 All rows checked, query ends

Variable Tracker

Variable	Start	After 1	After 2	After 3	After 4	After 5	After 6	Final
Current Row	None	Alice	Bob	Amanda	Charlie	Albert	David	None
Match Result	None	Yes	No	Yes	No	Yes	No	None
Included Rows	[]	[Alice]	[Alice]	[Alice, Amanda]	[Alice, Amanda]	[Alice, Amanda, Albert]	[Alice, Amanda, Albert]	[Alice, Amanda, Albert]

Key Moments - 3 Insights

Why does 'Bob' not appear in the results even though it has a 'b'?

The LIKE pattern 'A%' means the name must start with uppercase 'A'. 'Bob' starts with 'B', so it does not match (see execution_table row 2).

What does the '%' symbol mean in the LIKE pattern?

The '%' means any sequence of characters can follow after 'A'. So names starting with 'A' and any characters after match (see execution_table rows 1, 3, 5).

Is the LIKE pattern case sensitive?

Yes, in standard SQL LIKE is case sensitive unless the database uses case-insensitive collation. Here, 'A%' matches uppercase 'A' only (see 'Alice' vs 'alice').

Visual Quiz - 3 Questions

Look at the execution_table, what is the Match Result for 'Charlie'?

A Yes

B No

C Maybe

D Not checked

💡 Hint

Check the row with 'Charlie' in the execution_table under 'Match Result' column.

At which step does the query include the row 'Albert'?

A Step 5

B Step 3

C Step 4

D Step 6

💡 Hint

Look at the 'Included Rows' variable_tracker after each step.

If the LIKE pattern changed to '%a', which rows would match?

A Names containing 'a' anywhere

B Names starting with 'a'

C Names ending with 'a'

D Names exactly 'a'

💡 Hint

The '%' means any characters before 'a', so names ending with 'a' match.

Concept Snapshot

WHERE with LIKE pattern matching:
- Syntax: WHERE column LIKE 'pattern'
- '%' matches any sequence of characters
- '_' matches exactly one character
- Case sensitivity depends on DB
- Filters rows matching the pattern
- Useful for partial text search

Full Transcript

This visual execution shows how a SQL query with WHERE and LIKE pattern matching works. The query filters rows from a table by checking if a column's value matches a pattern. The '%' symbol means any characters can follow or precede. Each row is checked one by one: if it matches, it is included; if not, excluded. The example uses names starting with 'A'. The execution table tracks each row's check and action. The variable tracker shows how the current row and included rows change step by step. Key moments clarify common confusions like case sensitivity and pattern meaning. The quiz tests understanding by referencing the execution visuals. This helps beginners see exactly how LIKE filters data in SQL.