Python · Theory

UPDATE

Theory

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UPDATE

UPDATE is about talking to a database from Python. Pattern is always: connect → cursor → execute → fetch or commit → close.

For UPDATE: use ? placeholders (or the driver’s params). Never build SQL with + user text — that is injection. sqlite3 is in the stdlib for practice; MySQL/Mongo need a driver.

UPDATE on the board — insert Asha, select her back, print the name. Same idea on MySQL. Close the connection.

Output — 90. UPDATE then SELECT.

Exam tip

Steps in order: connect → execute → fetch/commit → close. Mention placeholders.

Example

# UPDATE
import sqlite3
con = sqlite3.connect(":memory:")
cur = con.cursor()
cur.execute("create table t(name text, marks integer)")
cur.execute("insert into t values('Asha', 80)")
cur.execute("update t set marks=? where name=?", (90, "Asha"))
print(cur.execute("select marks from t").fetchone()[0])
con.close()

Output: 90. UPDATE then SELECT.

Short notes

DefUPDATE uses connect + cursor + SQL/API.
RuleUPDATE — parameterized queries. Never + user text into SQL.
RememberUPDATE — commit after write. close when done.
TrapUPDATE — open connections left hanging; passwords in source.

# UPDATE import sqlite3 con = sqlite3.connect(":memory:") cur = con.cursor() cur.execute("create table t(name text, marks integer)") cur.execute("insert into t values('Asha', 80)") cur.execute("update t set marks=? where name=?", (90, "Asha")) print(cur.execute("select marks from t").fetchone()[0]) con.close()

UPDATE

Example

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UPDATE

Example

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Questions