87 lines
2.2 KiB
Markdown
87 lines
2.2 KiB
Markdown
UPDATE changes the values of the specified columns in all rows that satisfy the condition.
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More about UPDATE statement in PostgreSQL: https://www.postgresql.org/docs/11/sql-update.html
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Following clauses are supported
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- UPDATE(columns...) - list of columns to update
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- SET(values...) - list of values for columns
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- MODEL(model) - list of values for columns will be extracted from model object
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- WHERE(condition) - row condition to update
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- RETURNING(columns...) - list of columns to return as statement result
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_This list might be extended with feature Jet releases._
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## Example
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```
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// replace all Bing links with Yahoo
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updateStmt := Link.
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UPDATE(Link.Name, Link.URL).
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SET("Yahoo", "http://yahoo.com").
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WHERE(Link.Name.EQ(String("Bing")))
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```
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Debug sql of above statement:
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```sql
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UPDATE test_sample.link -- 'test_sample' is name of the schema
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SET (name, url) = ('Bong', 'http://bong.com')
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WHERE link.name = 'Bing';
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```
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Short-hand notation to extract model data for column values:
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```
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yahoo := model.Link{
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URL: "http://www.yahoo.com",
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Name: "Yahoo",
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}
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updateStmt := Link.
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UPDATE(Link.Name, Link.URL, Link.Description).
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MODEL(yahoo).
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WHERE(Link.Name.EQ(String("Bing")))
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```
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`Link.Name, Link.URL, Link.Description` - can be replaced with Link.MutableColumns. All columns minus primary key columns.
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Primary key columns are not updated usually.
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```
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updateStmt := Link.
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UPDATE(Link.MutableColumns).
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MODEL(yahoo).
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WHERE(Link.Name.EQ(String("Bing")))
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```
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### Execute statement
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To execute update statement and get sql.Result:
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```
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res, err := updateStmt.Exec(db)
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```
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To execute update statement and return row records updated, statement has to have RETURNING clause:
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```
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updateStmt := Link.
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UPDATE(Link.MutableColumns).
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MODEL(yahoo).
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WHERE(Link.Name.EQ(String("Bing"))).
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RETURNING(Link.AllColumns)
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dest := []model.Link{}
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err := updateStmt.Query(db, &dest)
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```
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Use `ExecContext` and `QueryContext` to provide context object to execution.
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Update example SQL table:
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```sql
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CREATE TABLE IF NOT EXISTS link (
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id serial PRIMARY KEY,
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url VARCHAR (255) NOT NULL,
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name VARCHAR (255) NOT NULL,
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description VARCHAR (255)
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);
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```
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